had + past participle
过去完成式是不能单独用的。我们用的时候，必须有另一个事件。也就是说，假如我们有两件事 A 和 B，两件事都发生在过去，但 A 发生在 B 以前，A 应该用过去完成式，B 则用过去式。以下是几个例子：
He had studied Chinese before he came to Taiwan.
He had worked before he decided to go to college.
I had been to Ireland before I wrote this book about Ireland's people.
I had studied calculus before I got into college.
It had already snowed before Monday.
如果我们要强调较早发生事件的连续性，我们可以用过去完成进行式。占去完成进行式和现在进行式惟一不同的地方是 verb to have 的地方一定要用had 。以下是一些过去完成进行式的例子：
1. I had been watching TV before you called me.
2. I had been working hard in a company for many years before I went to college.
3. He had been studying before he went to class.
4. He had been driving all day before he went to sleep.
那时以前 那时 现在
a. 在told, said, knew, heard, thought等动词后的宾语从句。
She said (that) she had never been to Paris.
When the police arrived, the thieves had run away.
c. 表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示"原本…，未能…"
We had hoped that you would come, but you didn't.
3) 过去完成时的时间状语before, by, until , when, after, once, as soon as。
He said that he had learned some English before.
By the time he was twelve, Edison had began to make a living by himself.
Tom was disappointed that most of the guests had left when he arrived at the party.