一、情态动词主要用来表示说话人的看法、态度等
1. can (could)
1) 表示能力，could主要指过去时间。例如：
① Two eyes can see more than one. 两只眼比一只眼看得清。
② Could the girl read before she went to school? 这女孩上学前能识字吗？
因为can不能和其他助动词连用，所以表示将来式时用will be able to
例：You will be able to skate after you have practiced it two or three times.
注意：Can表示一贯的能力，be able to表示客观能力和通过努力可以达到的能力
I can’t swim. But I am sure I will be able to swim through more practicing.
The fire spread through the hotel, but everyone was able to get out
2) 表示允许。例如：
① Can I have a look at your new pen? 我可以看一看你的新钢笔吗？
② He asked whether he could take the book out of the reading—room. 他问他可不可以把书带出阅览室。
3) 表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。例如：
① Where can (could) they have gone to? 他们会去哪儿了呢？
② How can you be so careless? 你怎么这么粗心？
4) 比较委婉客气地提出问题或陈述看法。例如：
① Can (Could) you lend me a hand? 帮我一把好吗？.
② I’m afraid we couldn’t give you an answer today. 恐怕我们今天不能给你答复。
Could/can+have done 结构表示对过去发生的事情的“怀疑”或“不肯定”。could 加完成式还用于肯定句时一般表过去可能完成而却未完成的动作。
Can they have won the basketball match？
他们赢了那场篮球赛吗？
What you referred to just now can have made her very sad.
你刚刚所谈到的可能令他很伤心。
You could have completed the task a little earlier.
你本来能早点完成任务的。（但事实上并没有提前完成任务）
I could have passed my examination easily but I made too many stupid mistakes.
我本可以轻易通过考试，但我犯了太多不该犯的错误。
如表具体做某一件事的能力时，则须用be able to .
He was able to translate the article without a dictionary.
他可以不用词典翻译那篇文章。
2．may (might)
1) 表允许，might可以指过去时间，也可指现在时间，语气更委婉。例如：
① You may take whatever you like.你喜欢什么就拿什么。
② May (Might) I ask for a photo of your baby? 我可以要一张你宝宝的照片吗？
2)在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly. / Please don’t. / You’d better not. / No, you mustn’t.等，以免显得太严峻或不客气。
3)may /might 推测性用法可能
He may be right. He may not come today (可能不) He may /might come tomorrow.
注意: (1)只用于肯定和否定句中,不用于疑问句中。
(2) might 比may可能性更小
He might get a job. He may get a job.
(3) may no 可能不can not不可能
He may not come . He can’t come
4)表建议（可和as well 连用）
You may（might）as well stay where you are. 你还是原地待着好。
（may as well 有―还是……的好‖的含义）
5)表祝愿
May you be happy!
6). might表过去的―可能‖和―允许‖多用于间接引语。
She said that he might take her dictionary. 她说他可以拿她的词典去用。
除在间接引语中外，might一般不表示过去的“可能”与“许可”。表过去的“可能”可用could，表过去的“许可”可用were (was) allowed to。
7)might表现在的“可能‖，其可能性要比may小。
Electric irons could be dangerous; they might give you a severe shock.
8)may (might) + have +done 表示对过去发生行为的推测，含有―想必‖、―也许是‖的意思。
It may have been true. 这事也许是真的。He might not have settled the question. 他可能尚未解决那个问题。3. must
1)表示义务。意为―必须‖（主观意志）。例如：
We must do everything step by step .我们必须按部就班地做一切事情。
Why must you always bother me? 为什么你偏要打扰我呢。
2)must be + 表语的结构，通常表示猜测，含有―一定‖之意。（只用在肯定句中）
He must be an honest boy.他一定是个诚实的男孩This must be your room.这一定是你的房间。
3)must 的否定式有两个：当回答由must引起的问题时，否定答复要用needn’t或don’t have to 表示―不必‖、―无须‖、―用不着‖、―不一定‖的意义。当表示―不应该‖、―不许可‖、―禁止‖时，就用must not。
Must I go tomorrow?明天我必须去吗？Yes, please. No , you needn’t.
4)must +have +过去分词的结构，常用在肯定句中，表示对过去发生行为的推测，含有―一定‖、―准是‖的意思。否定和疑问句用can。
She must have studied English before.她以前一定学过英语。
5) 区别：have to的含义与must是很接近的,只是have to 比较强调客观需要，must着重说明主观看法。
I must clean the room.（主观想法）I have to clean the room.（客观需要）
另外，have to 能用于更多时态：
We had to be there at ten .我们得在十点钟到那里。We will have to reconsider the whole thing.
have to 的否定式：don’t have to do 表示―不必做……‖之意。
4.shall
1) 表征询意见，用于第一、第三人称疑问句。例如：
① Shall I get you some tea? 我给你点茶好吗？
② Shall the boy wait outside? 让那男孩在外面等吗？
2)表说话人的意愿，有―命令、允诺、警告、决心‖等意思，用于第二、第三人称陈述句。
例如：
① You shall do as I say. 按我说的做。（命令）
② You shall have my answer tomorrow. 你明天可以得到我的答复。（允诺）
③ He shall be sorry for it one day, I tell you. 有一天他会后悔的，我告诉你。（警告）
④ Nothing shall stop us from carrying out the plan. 什么也不能阻止我们执行这项计划。（决心）
5. should
1)用于第一人称疑问句中询问对方的意愿，但语气较委婉温和，如：
What should we do now? 我们现在该怎么办？
2)表示应该、必须，常与must 换用。例如：
We should (must) master a foreign language at least.
3）（表示不确定）万一。例如：
① If I should see him, I'll tell him. 万一我见到他，我就告诉他。
② If it should rain tomorrow, the sports meeting would be postponed. 万一明天下雨。。。
4)―should+be+表语‖的结构，表示推测或惊奇。例如：
They should be back by now. 他们现在应该回来了吧。
I am sorry that she should be so careless. 我感到遗憾她竟会那样粗心。
5)―should+have+过去分词‖的结构，表示过去该做而实际上尚未做的动作或行为；其否定则表示发生了不应该发生的行为。其同义结构―ought to have +过去分词‖,表示过去―早应该‖、―本当‖之意，语气较强。例如：I should have thought of that. 这一点我是应当想到的。（但没想到）
They should not have left so soon.他们不应当走得这么早。（但已走了）
6) 在―It is natural (strange, natural, necessary, surprised, impossible, important ) that……‖句型中，主语从句中的谓语动词要用should +动词原形‖表示―理所当然‖、―奇怪‖、―必要‖、―惊异‖等的意思。在lest（以免）、for fear (that) (以防)、in case（以备万一）等之后也要用should+动词原形;在advise, sugest, order, demand, request 等的从句中should+do‖例如：
It is necessary that he(should) be sent there at once.
It is strange that he should say so. 他会说这样的话真是奇怪。
6.will和would的用法
1）表示意志，决心或愿望。例如：
Surely we will support all the people in the world in their struggle for peace.
He would not let me try it . 他不肯让我去试。
2）will表示经常性、习惯性、倾向性，would表示过去的习惯行为。
He will sit there hour after hour looking at the traffic go by.
He would come to see me when he was in Beijing.
3）用于第二人称作主语的疑问句中，表示对对方的请求，would的语气比will委碗
Would/will you kindly tell me the way to the station? 请问到火车站怎么走？
4）表可能性
This will be the book you are looking for. 这可能就是你要找的书。She would be about 60 when she died.
7.ought to
表义务，意为―应该‖（因责任、义务等该做），口气比should稍轻。例如：
① You are his father. You ought to take care of him.你是他父亲，应当管他。
② You oughtn’t to smoke so much. 你不应该抽这么多烟。
8. used to
1）表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。例如：i
① There used to be a building at the street corner, but it has been pulled down.
② I usedn’t (didn’t use) to smoke. 我过去不抽烟。j }F
③ Used you (Did you use) to go to school on foot? 你过去常步行去学校吗？
2）used to +v, be used to +v-ing和be used to +v
used to +v意为―过去常常‖，―过去一直‖；be used to +v-ing / n（名词）意为―习惯于‖；be used to +v意
为―被用来（做某事）‖。
例：He used to smoke. Now he doesn’t.He’s quite used to hard work / working hard.
The knife is used to cut bread.
9.特殊情态动词need和dare的用法：
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
need 情态动词实义动词
现在时You need (not) do
He need (not) do You (don’t) need to do
He needs (doesn’t need) to do
过去时You needed (didn’t need) to do
He ne eded (didn’t need) to do
将来时You need (not) do
He need (not) do You will (not) need to do He will (not) need to do
dare 情态动词实义动词
现在时dare to/
daren’t/dare not do
Dare he do? dare/dares to do
do/does not dare (to) do
Do you/Does he dear (to) do?
过去时dared to/dared not do
Dared he do? dared to do/did not dare (to) do Did he dare (to) do
1) 用作情态动词。例如：|
You needn’t telephone him now. She dare not go out alone at night. 她晚上不敢一个人出去。
2) 用作实义动词。例如：
You don’t need to do it yourself. I dare say he’ll come again.我想他会再来（I dare say…为固定
二、情态动词表推测：
1.can 表示可能（理论上或是逻辑判断上）。例如：~,>_K
① He can’t (couldn’t) have enough money for a new car. 他不可能有足够的钱买新车。
② You mustn’t smoke while you’re walking around in the wood. You could start a fire. 在林子里走时勿吸烟，那样可能会引起火灾。
2.may 表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
① He may be at home. 他可能在家。\② She may not know about it.
3. must 表示揣测。意为―想必、准是、一定‖等，只用于肯定句。
① He must be ill. He looks so pale. 他准是病了。他的脸色苍白。
② She’s wearing a diamond necklace. She must have a lot of money.
4. should 表推测，意为―想必一定、照说应该、估计‖等。例如：
① The film should be very good as it is starring first-class actors. 这部新电影是一流演员主演的，估计拍得很好。
② They should be home by now. 照说他们现在应当已经到家了。
5. ought to 表推测，暗含很大的可能，语气较弱。例如：
① Han Mei ought to know his telephone number. 韩梅该知道他的电话号码。
② There’s a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天应该是个好天。
6. could可能性不大，语气较弱。7 might 可能性最小，语气最弱。
表示可能性大小的顺序为：must > will > would > ought to > should > can > could> may> might
7.would rather, would sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well等可用作情态动词。例如：
1）The soldier would sooner die than surrender. The brave soldier would as soon die as yield to such an enemy. I’d rather walk than take a bus.
If you don’t like to swim, you may just as well stay at home.
2)would (had) rather, would (had) sooner, would (just) as soon后可跟that 引导的从句，that 常省去，从句要用虚拟语气。对现在和将来的假设用过去时，对过去的假设用过去完成时。例如：
I would rather you came on Sunday. I would sooner you hadn’t asked me to speak yesterday.
8.表推测的情态动词句子的反意疑问句
He must/may be in the room, isn’t he?He can’t be in the room, is he？
He must have finished the work, hasn’t he?He may have done the work last night, didn’t he?
结构：
1情态动词+ 动词原形（对现在和将来的动作进行推测）
He must understand that we mean business.
2情态动词+ be +doing (对正在发生的动作进行推测)
---Where is LiLei ? ---- He may be studying at school.
3.情态动词+ have +done ( 对过去的动作进行推测)
must have done 一定干了某事could have done 可能干了某是或本可以干了某事
may/might have done 也许已经干了某事should/ ought to have done 本应该做了某事可是没有做
need not have done 本不必干了某事表示过去做了某事，但没有做的必要，意为―本没必要…‖You needn’t have waken me up; I don’t have to go to work today
had better have done 最好干了某事would rather have done 宁愿干了某事
would like / love have done 本想干了某事其实未干Since the road is wet, it must have rained last night.
备注：态动词+ have +done 反义问句的结构由有无时间状语来决定。
Lucy must have worked last night, didn’t she?
Lucy must have worked , hasn’t she?
4.情态动词+ have been + v-ing形式（表示推测或评论过去某动作是否正在进行或一直在进行）
They should have been meeting to discuss the problem.
三、情态动词其它用法
1. cannot but do sth. 表示不得不，只好I cannot but choose to go.
2. may well +动词原形完全能，很可能He may well be proud of his son.
3. may as well 最好……We may as well stay where we are.
4 cannot ( 或never 等否定词)与enough 表示再……也不为过You cannot be careful enough.
情态动词练习题
1. Jack described his father, who _______a brave boy many years ago, as a strong–willed man
A. would be
B. would have been
C. must be
D. must have been
2.You_______ buy a gift, but you can if you want to.
A. must
B. mustn't
C. have to
D. don't have to
3. I have told you the truth. ______ I keep repeating it?
A Must
B Can
C May
D Will
4. I_______ have watched that movie —it’ll give me horrible dreams.
A. shouldn’t
B. needn’t
C. couldn’t
D. mustn’t
5. Mark _______ have hurried. After driving at top speed, he arrived half an hour early.
A. needn’t
B. wouldn’t
C. mustn’t
D. couldn’t
6. _______ I take the book out?
—I'm afraid not.
A. Will
B. May
C. Must
D. Need
7.Just be patient .You ______ expect the world to change so soon .
A. can’t
B. needn’t
C. may not
D. whether
8.—I haven’t got the reference book yet, but I’ll have a test on the subject next month.
—Don’t worry. You______ have it by Friday.
A.could
B. shall
C. must
D. may
9.May I take this book out of the reading room?
No, you______ . You read it in here.
A. mightn’t
B. won’t
C. needn’t
D. mustn’t
10.Doctors say that exercise is important for health, but it _______ be regular exercise.
A．can B．will C．must D．may
11.---Good morning. I've got an appointment with Miss Smith in the Personnel Department.
--Ah, good morning. You _______ be Mrs. Peters.
A. might
B. must
C. would
D. Can
12.―You ____ have a wrong number,‖ she said. ―There’s no one of that name here.‖
A. need
B. can
C. must
D. would
13.---Sorry, Professor Smith. I didn't finish the assignment yesterday.
---Oh, you ____ have done it as yesterday was the deadline.
A.must
B. mustn't
C. should
D. shouldn't
14. Bob would have helped us yesterday, but he-_______
A. was busy
B. is busy
C. had been busy.
D. will be busy
15. John went to the hospital alone. If he_______ me about it, I would have gone with him.
A. should tell
B. tells
C. told
D. had told
16. George is going to talk about the g eography of his country, but I’d rather he_______ more on its culture.
A. focus
B. focused
C. would focus
D. had focused
17.If we ___ the other road, we might have arrived here in time for the meeting.
A. take
B. had taken
C. took
D. have taken
18.--The weather has been very hot and dry.
--Yes. If it had rained even a drop, things would be much better now! And my vegetables .
A. wouldn't die
B. didn't die
C. hadn't died
D. wouldn't have died
19．Had I known about this computer program, a huge amount of time and energy . A．would have been saved B．had been saved C.will be saved D．was saved
20. It’s the office! So you___ know eating is not allowed here. —Oh, sorry.
A. must
B. will
C. may
D. need
21. What do you mean, there are only ten tickets? There___ be twelve.
A. should
B. would
C. will
D. shall
22. —I don’t care what people think.—Well, you _______
A. could
B. would
C. should
D. might
23.I can’t find my purse anywhere. —You have lost it while shopping.
A.may
B.can
C.should
D.would
24.It is usually warm in my hometown in March，but it be rather cold sometimes.
A.must
B.can
C.should
D.would
25.—How’s your tour around the North Lake? Is it beautiful?
—It____ be，but it is now heavily polluted.
A.will
B.would
C.should
D.must
26.What’s the name? Khulaifi. ____ I spell that for you?
A.Shall
B.Would
C.Can
D.Might
27.John，look at the time. ____ you play the piano at such a late hour?
A.Must
B.Can
C.May
D.Need
28.Catherine，I have cleaned the room for you. —Thanks. You____ it.I could manage it myself.
A. needn’t do
B. needn’t have done
C.mustn’t do
D.shouldn’t have done
29.I’ll tell Mary about her new job tomorrow. —You____ her last week.
A.ought to tell
B.would have told
C.must tell
D.should have told
30.—Excuse me.Is this the right way to the Summer Palace?
—Sorry，I am not sure. But it____ be.
A.might
B.will
C.must
D.can
1. D. 考查情态动词推测用法。句意为“杰克把他的父亲描述为一个意志坚强的人，他的
父亲多年前肯定很勇敢。”用must have been表示对过去事情的肯定推测。
2. D情态动词don’t have to 意为“没有必要”，符合语境，句意为：“你没有必要买礼物，但如果你想买的话，你也可以买。”
3. A考察情态动词的用法。must 必须, 一定can 可以, 能够may 也许will 意愿, 倾向性动作, 前半句说我告诉你事实了, 这里用的是现在完成时, 表示过去的动作对现在造成了影响, 既然我已经说了, 我还必须重复一遍吗？
4.A本题考查情态动词的用法。句意应为“我本来不应该看那部电影的----它会使我做噩梦的。”表示“本来不应该做而做了某事”用shouldn’t have done, 所以A项正确。
5. A. 考查情态动词。迈克本来不必要那么忙的。这么高速驾驶之后，他早半个小时到达了。根据后面的语境，提前半个小时到达，说明Mark本来不必那么匆忙，所以用needn’t have done 结构，表示“本来不必要做某事的而实际上做了”。
6.B考查情态动词。表请求可用情态动词can, may, could, might ,表允许用can, may.
句意为：“我可以将这本书带出去吗？”“恐怕不行”。故应选表情请求的情态动词may。
7. A耐心一点儿，你不能期望世界变化如此快。通过选项此题考察情态动词，can't在否定句中可以表示推测，译为不可能，，可以表示能力，译为不能够，也可以表示命令，不允许，但是语气比mustn't弱，具有劝慰的意思，根据句意此题中选择A，can't表示劝慰。
8. B，shall在第二人称中表示允诺，还可以表示强制，命令，威胁，警告。还有在法律条
文中的要求或规定。
9. D情态动词。英语中用could，might表示询问或征求意见的问句中，肯定性应答
要用can或may来代替could或might，而may或might征求意见的问句否定应答时要用mustn’t，故本题选D。
10C句意：医生说锻炼对身体重要，但是必须是有规律的锻炼。考查情态动词。Can一般表示“可能，或能力”；will表示“意志”；may表示“许可，可能”；must表示“必须”。
11. B本题考查情态动词在语境中的运用。第一个说话人说和史密斯小姐有约，那下面的人就回应说，"那您一定就是Mrs. Peters了"因此排除A,C.D
12. C情态动词
13. C本题考查的是虚拟语气此处表示和过去事实相反的情况，应该用should + have + 过去分词。本来应该做，而未做
14. A. 本题考查虚拟语气与时态。前句表示对过去的虚拟，而but之后表示过去的客观事实，故用一般过去时态。
15. D. 考查虚拟语气。约翰独自去了医院。如果他告诉我的话，我会跟他一起去的。
解析：前一句是陈述语气，说明动发生在过去，而且后一句的主句已经是would have gone 说明是与过去事实相反的虚拟语气。与之对应的从句结构，应该用had +过去分词。
16 B 解析：would rather后应用虚拟语气，表示与现在时间相反，用动词的过去式
17. B.考查虚拟语气。所填词做虚拟语气中条件状语从句的谓语，根据主句的谓语动词
形式might have arrived可知题干是与过去事实相反，故所填部分用had+过去分词形式
18. D本题考查虚拟语气中对过去的虚拟。第二个说话人的If条件句是我们选择正确答案的关键。要是当时下雨了，现在的情况就好的多了！我的蔬菜也就不会死了。过去没有下雨，所以我的蔬菜干死了也是发生在过去。而将句子还原则为If it had rained even a drop, my vegetables wouldn't have died.If+ had done,主句为couldn’t/ shouldn't/ wouldn't have done.
19．A本题考查虚拟语气。根据句子的倒装特征判断此处是省略了if的虚拟语气，原形是：If I had known about this computer program, a huge amount of time and energy.句意为：如果我早知道这个电脑程序，就可以节省大量的时间和精力了
20. A 句意为这是办公室！因此你必须知道吃的不允许带到这里。must表示“绝不”的意思。
21.A 解析你这是什么意思，只有十张票吗?应该有十二人。should表示“应该，应当”。
22. C考查情态动词的用法。答话的人提了一个建议——你应该关注别人对你的评价的。should可以用来向别人提建议，所以答案为：C
23. A解析may表达推测之意，意为“可能……”。
24.B must必然，一定；can可能；should应该；would（过去）将，总会。本题提供的语境是“有时可能会……”。
25. C考查情态动词的区别。will可用来表示“意愿；客观必然性等”；would可表示“意愿；过去常常（现在也可能是那样的）”；should表示“应该，理应”；must表示“必然；一定，准是”。结合语境可知，此处用should表示虚拟。句意为：“这本来应该是美丽的，但是现在它被严重污染了。”
26.A shall在问句中征求对方意见，主要用于第一人称。答语句意为：“我给你拼写一下好吗？”
27. A解析must在此处显示出说话人的不快，有“难道非要”的意思。
28.B考查情态动词的完成式和一般式的区别。needn’t do不需要做……；mustn’t禁止做……，都用于现在的动作；needn’t have done表示做了本来不必去做的事；shouldn’t have done 是本不该做却做某事。
29. D “情态动词+have done”构成的虚拟语气用法。答语句意为：你本该上周就告诉她(其实没告诉她)。
30.A解析“I am not sure”说明说话者对情况没有把握，推测语气较弱，使用might。