主句中的动词、名词、形容词如表示要求、建议、命令或想里等含义，与其相关的名词性从句（主语从句、宾语从句、表语从句和同位语从句）中的谓语动词要用虚拟语气。现在或将来情况时，谓语动词用should/would +动词原形 (should/would经常省略)的形式。如果表示过去的情况，谓语动词要用should/would + have done的形式。
宾语从句中虚拟语气
- 用于表示建议、命令、要求、愿望等意义的动词后的宾语从句中。
- He suggested that we should/would go there at once. 他建议我们立刻去那里。
- She begged that he should/would have stayed with her. 她恳求他本应该留下来陪她。
- The teacher demanded that the students should/would hand in their homework on time. 老师要求学生按时交作业。
- He advised that we should/would have gone there. 他建议我们本应该去那里。
- He commanded that the soldiers should/would march at once. 他命令士兵们立刻出发。
- wish后的宾语从句也可以表示不可实现的愿望，这时谓语动词要用虚拟语气，表示与现在或过去的事实相反。
- I wish I had a car. 我希望我有一辆车。（与现在事实相反）
- I wish you were/was here. 我希望你在这里。（与现在事实相反）
- I wish I had studied harder. 我希望我学习更努力。（与过去事实相反）
- I wish it had not rained yesterday. 我希望昨天没有下雨。（与过去事实相反）
- would rather后面宾语从句虚拟语气，是指在表示偏好或愿望的would rather后面接一个从句，从句的谓语动词用过去式或过去完成时，表示现在或过去的情况。
- I would rather you stayed at home. 我宁愿你呆在家里。（现在）
- She would rather (that) her mother hadn’t interfered with her marriage. 她宁愿她母亲没有干涉她的婚姻。（过去）
- He would rather we didn’t tell anyone about it. 他宁愿我们不要把这件事告诉任何人。（现在）
主语从句中虚拟语气
- 用于表示建议、命令、要求、愿望等意义的名词后的同位语从句中
- It is his suggestion that we should/would leave early. 这是他的建议，我们应该早点走。
- It is his demand that the workers should/would get higher pay. 这是他的要求，工人们应该得到更高的工资。
- It is ordered that he should/would leave at once. 命令他立刻离开。
- It is necessary that he should/would be present. 他必须出席。
- 表示惊讶
- It is amazing that he should have won the prize. 真令人惊讶，他竟然赢了奖。
- It is odd that she should have left without saying goodbye. 真奇怪，她竟然没有说再见就走了。
- It is a wonder that he should have survived the accident. 真是个奇迹，他竟然在事故中幸存下来。
表语从句中虚拟语气
在表示建议、劝告、命令等含义的名词后的表语从句中，谓语动词要用“should+动词原形”结构，表示现在或将来的情况。
- His suggestion is that we should/would go there tomorrow. 他的建议是我们明天去那里。
- The order is that the soldiers should/would leave at once. 命令是士兵们立刻离开。
- The rule is that the students should/would not cheat in the exam. 规定是学生们不得在考试中作弊。
同位语从句中虚拟语气
- It is his wish that he should/would become a doctor. 他的愿望是他能成为一名医生。
- The proposal that the project should/would be postponed is unacceptable. 项目要推迟的提议是不可接受的。
- The idea that we should/would help each other is good. 我们应该互相帮助的想法是好的。