虚拟语气，顾名思义就是假设的或虚构的语气。因此在使用中与陈述语气有本质上的区别。以下是我对虚拟语气用法的总结与归纳，仅供读者参考。
一、虚拟语气在宾语从句中的应用
1.“wish+宾语从句”表示不能实现的愿望，译为“可惜……”、“悔不该……”、“但愿……”等。表示现在不能实现的愿望，从句的谓语动词用过去式；表示将来不能实现的愿望用“would（could）+动词原形”；表示过去不能实现的愿望用“had+过去分词”或“would（could）+ have+过去分词。”
①I wish I were as tall ?as Yao Ming.
②I wish every family had a big house with a beautiful garden.
③I wish you could come back before Christmas.
④I wish you had come to our English party yesterday evening.
2.用于某些表示请求命令等动词的宾语从句中，从句中的谓语动词由“should+动词原形”构成，should可以省去。常见动词有insist,order,demand,advise,suggest,propose,require,ask,request,desire等。
①The doctor ordered that she (should) stay in bed for a few days.
②I required that they (should) leave at 8 this evening.
但是suggest作“建议”讲，宾语从句用虚拟语气；若作“暗示、表明”讲，则用陈述语气。
Her face suggested that she was angry.
Insist作“力言，强调”讲时，宾语从句不用虚拟语气。只有作“坚持（认为）”、“坚持（应该）”讲时宾语从句才用虚拟语气。
They insisted that she went there.他们坚持说她到那里去了。“去那里”是事实，用陈述语气。
They insisted that she should go there.他们坚持要她去那里。“坚持”是一种想法，用虚拟语气。
二、虚拟语气在表语从句和同位语从句中的应用
advice,idea,order,demand,plan,proposal,request,su
ggstion等名词的表语从句和同位语从句时,其谓语动词要用虚拟语气结构”(should)+动词原形”。
①We all agreed to his suggestion that we (should)go to Beijing for sightseeing.(同位语从句)
②The officer’s order was that all the soldiers should get to the top of the hill before dark.(表语从句)
三、虚拟语气在as if（as though）引导的表语从句或状语从句中的应用
(1)与现在事实相反用动词过去式(be一律用were)
It seems as if it were spring now.
He is running about as if he were a mad man.
(2)与过去事实相反,用“had+过去分词”
①He spoke as though he had known it.
②He speaks English so fluently as if he had studied English in England.
③When a chopstick is partly in a glass of water as if it were broken.
四、虚拟语气在主语从句中的应用
在It is necessary /important/strange/natural;
It is requested/suggested/desired/proposed;
It is a pity; It is a shame等主语从句中谓语动词用should+动词原形或只用动词原形，表示惊奇,不相信、惋惜、理应如此等。
①It is necessary that we(should)clean the room every
day.
②It is strange that he (should) have so many friends.
③It has been decided that the meeting (should)be put off till tomorrow.
④It’s natural that he should say so.
五、虚拟语气在定语从句中的应用
常见句型有It is（high）time（that）……中，谓语动词用过去式或should+动词原形, should不能省略，意为“该做某事的时候了”。
It is time that we left (should leave).
It is high time that they should finish their homework.
六、虚拟语气在if only从句中的应用
if only意为“如果…就好了”、“要是…该多好啊！”
①If only I had met her early .如果早点遇到她该多好！
②Look at the trouble I am in !If only I had followed your advice.
七、虚拟语气在条件状语从句中的应用（如下图）
情况从语中谓语动词构成主句中谓语动词构成
①与现在事实相反动词用过去式，be动词一般 用were would+动词原形
should+动词原形
could+动词原形
might+动词原形
②与过去事实相反过去完成时had done would
should+have done
could
might
③与将来事实相反①过去式did/were
②should+v
③were to+v would
should
could+动词原形
might
①If she knew about it,she would come.
②If I were you,I wouldn’t go there.
③If you had come earlier,you would have met her.
④If it should rain,the crops would be saved.
⑤If it should be free tomorrow,I would go with you.
八、混合条件句。有时主句与从句的谓语动词并不相互呼应，这种条件句叫混合条件句。
①He would pass the exam if he had taken my advice.
②If he were alive now,he might have finished the scientific research three years ago.
③If I were you,I wouldn’t have watched TV last night.
九、隐含条件句
1、由with，without，but for等介词或介词短语来表示隐含条件。
①With your help,we might finish the work earlier.
②Without water,there would be no life.
2、用连词or，otherwise，but，however等表示隐含条件。
①I was really busy,otherwise I would have gone withyou.
②She would have come here,but she was too busy with her homework.
十、虚拟语气的省略情况
如果虚拟条件句的谓语部分有were，had和should时，可省略if，把were，had和should放在主语前。
①Had you not helped me,I should have failed.
②Were I in school again,I would work harder.
③Should it rain tomorrow,we would put off the visit to Bridge.
