1） 概念：表示过去的过去
----|----------|--------|----> 其构成是had +过去分词构成。
那时以前 那时 现在
2） 用法
a. 在told, said, knew, heard, thought等动词后的宾语从句。例如：
She said （that）she had never been to Paris. 她告诉我她曾去过巴黎。
b. 状语从句
在过去不同时间发生的两个动作中，发生在先，用过去完成时；发生在后，用一般过去时。例如：
When the police arrived, the thieves had run away. 警察到达时，小偷们早就跑了。
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…"。例如：
We had hoped that you would come, but you didn't. 那时我们希望你能来，但是你没有来。
3） 过去完成时的时间状语before, by, until , when, after, once, as soon as。例如：
He said that he had learned some English before. 他说过他以前学过一些英语。
By the time he was twelve, Edison had began to make a living by himself. 到了十二岁那年，爱迪生开始自己谋生。
Tom was disappointed that most of the guests had left when he arrived at the party.
汤姆失望了，因为他到达晚会时，大部分客人已经走了。
典型例题
The students ___ busily when Miss Brown went to get a book she ___ in the office.
A. had written, left B，were writing, has left C. had written, had left D. were writing, had left
答案D. "把书忘在办公室"发生在"去取书"这一过去的动作之前，因此"忘了书"这一动作发生在过去的过去，用过去完成时。句中when表示的是时间的一点，表示在"同学们正忙于……"这一背景下，when所引导的动作发生。因此前一句应用过去进行时。
注意： had hardly… when 还没等…… 就……。例如：
I had hardly opened the door when I he hit me. 我刚打开门，他就打了我。
had no sooner…than 刚…… 就……。例如：
He had no sooner bought the car than he sold it. 他刚买了这辆车，转眼又卖了。