过去完成时(The Past Perfect Tense)：表示过去某一时间或动作以前，已经发生或完成了的动作对过去的某一点造成的某种影响或是结果，用来指在另一个过去行动之前就已经完成了的事件。它表示动作发生的时间是“过去的过去”，侧重事情的结果。
结构
主语+had+动词过去分词
①肯定句：主语+had+动词过去分词+其他.
②否定句：主语+had+not+动词过去分词+其他.
③疑问句：Had+主语+动词过去分词+其他?
肯定回Yes,主语+had.
否定回No,主语+hadn't.
④特殊疑问句：特殊疑问词或词组+had+主语+过去分词+其他？
⑤被动语态：主语+had(not) +been+动词过去分词+其他.
例句
过去完成时常用的时间状语有：
1. by the end of last+时间段. By the end of last term, we had learned 5000 new words.
2. By the time ***. +动词过去式如：The bus had already left by the time I got there.
3.By (the time of) last year ,we had built two bridges.
大部分情况下以一般过去时did/was/were结构做比较，常见句型总结如下：
1.“主语 +had done…, before 从句(did/was/were)”
例如：Fortunately, the population had left the village before the volcano erupted.(幸运的是，火山喷发前人们已离开了村庄。)
2.“主语 +had done…, when 从句(did/was/were)”
例如：They had already put the fire out when I returned to the village.(当我返回村子时，人们已将大火扑灭。)
3.“By the end of +名词(短语)，主语 + had done…”
例如：By the end of the day, most of the inhabitants had left their homes.(到这一天，大部分居民已离开他们的家园。)
4.“主句(had done), before + 过去时间状语 ”
例如：They had never seen so many of the locusts before.(他们以前从未见过如此多的蝗虫)
I had reached the station before six o'clock.
(六点之前我已到达车站。)
5.“By the time + 从句(did/was/were), 主语 + had done…”
例如：By the time we arrived, everyone had received medical care.(我们到达时，每个人已接受了医疗护理。)
6.“用在 It /This/That was the first…time + that 从句 (had done)中”
例如：It was the third time that he had made the same mistake. (这是他第三次犯同样的错误了。)