“情态动词+ have +过去分词”结构是高中英语中一个比较难理解的知识点。因此，有必要对此结构及其用法作一简要归纳，以利于同学们理解和全面掌握。
     1.“must + have +过去分词”，译为“一定……”，表示说话人通过就目前情况观察与分析，对过去发生的事情作出的肯定判断。如：
It must have rained last night, since the ground is wet.
地上是湿的，昨晚一定下雨了。
Her father thought that she must have met a fairly.
她爸爸认为她一定遇上了仙女。
Where is my knife? I must have lost it.
我的小刀到哪去了？我一定把它弄丢了。
I didn't hear the knock, I must have been asleep.
我没有听到敲门声，我一定是睡着了。
     2.“may + have +过去分词”，译为“可能已经……，也许已经……”，表示说话人通过就目前情况观察与分析，对过去发生的事情作出的可能性判断。如：
You may have noticed that the sun on a winter's afternoon is low on the horizon.
你可能已经注意到，冬天下午的太阳低低的，接近地平线。
He's not come yet. He may have missed his train.
他还没来。他也许没赶上那班火车。
     3.“might+ have+过去分词”，译为“其实（本来）可以……”，表示说话人对已经发生了的事提出委婉的批评意见。如：
He might have given you more help, even though he was very busy.
他本来可以多给你些帮助，尽管他很忙。
This might have cured your cough, if you had taken it.
如果你以前吃这种（药），你的咳嗽本来可以治好的。
说明：“might + have +过去分词”和“may + have +过去分词”通常可以互换。might表示的可能性比may更弱、更委婉。
     4.“can/could(not) + have +过去分词”，译为“决不会……，不太可能……”，表示对过去行为的怀疑或不肯定。如：
It can't have been lost in the post.
这东西决不会在邮电局里丢的。
He can't have taken it home.
他不可能把它带回家。
Could/Can they have completed their work so soon?
他们这么快就能完成任务（工作）吗？
His car isn't there. Can he have gone out?
他的车子不在。他是不是出去了？
     5.“should/ought to + have +过去分词”，译为“本应该……”，表示对过去事情的后悔或责备。如：
You should have handed in your homework yesterday afternoon.
你应该昨天就把作业交来。
This cupboard should not have been painted yellow.
这橱柜本不应漆成黄色的。
You ought to have watered the trees more often.
你本来应该更经常地给那些树浇水的。
说明：should与ought to 常可通用，只是ought to 比should 的口气更强些。
     6.“needn't + have+过去分词”，译为“本来不必……，其实不需要……”，表示做了本来不该做的事。如：
You needn't have called me on the phone last night.
昨晚你本来没有必要给我电话。
There was plenty of time. She needn't have hurried.
时间很充裕，其实她不必那么匆忙。
说明：与should have done 相比，needn't have done 没有“悔恨”和“责备”之意。