情态动词 基本含义 例句 must have done 肯定已经（过去极有可能发生） He must have forgotten the meeting. (他肯定是忘了会议。) may/might/could have done 可能已经（过去有可能发生） She might have missed the bus. (她可能没赶上公交车。) can't/couldn't have done 不可能已经（过去肯定没发生） He can't have left. His car is still here. (他不可能走了，车还在这儿。) should/ought to have done 本应该做（但实际没做） You should have told me earlier. (你本该早点告诉我。) shouldn't have done 本不该做（但实际做了） You shouldn't have said that. (你当时不该说那句话的。) could have done 本来能够做（但实际没做） I could have passed the exam. (我本来能通过考试的。) would have done 本来会做（常用于虚拟语气） I would have called you, but my phone died. (我本来会打给你，但手机没电了。) needn't have done 本不必做（但实际做了） You needn't have bought any milk. I already had some. (你本不必买牛奶的，我已经有了。) 总结：这个结构的核心是 情态动词 + 过去分词（have done），理解的关键在于区分情态动词本身是表示推测还是非现实的愿望/责。