完成式表示的动作或状态发生在谓语动词表示的动作或状态之前。下面举例说明一下。

　　如：

　　I am sorry to have kept you waiting. (=I am sorry that I have kept you waiting)

　　对不起，让你久等了。

　　注意：

　　若谓语表示“愿望、打算、意图”的动词时。

　　如hope，think，want，plan，expect，mean，

　　intend等，其后可以跟不定式的完成式表示“本来想要或打算做某事，而实际上未能实现”。

　　如：

　　We meant to have stopped him from doing such a thing.

　　不定式完成式的用法

　　1、表示发生在谓语动作之前的动作：

　　He seems to have caught a cold.

　　他似乎感冒了。

　　I hate to have quarreled with her.

　　我后悔和她吵架了。

　　I believe it to have been a mistake.

　　我相信这是一个错误。

　　You appear to have travelled quite a lot.

　　你似乎作过多次旅行。

　　I’m sorry to have given you so much trouble.

　　对不起给了你这么多麻烦。

　　It’s said to have been built in the Ming dynasty.

　　据说它是明朝修建的。

　　2、表示在某个给定的时间之前已完成的动作：

　　I hope to have finished the work by now.

　　我希望现在以前已完成这项工作。

　　3、表示过去未曾实现的想法和愿望：

　　I should like to have come earlier.

　　我本想早点来的。

　　We were to have been married last year.

　　我们本来打算去年结婚的。