1：表示过去某时正在进行的动作
过去进行时作这一用法时，通常也要把时间状语表示出来，或者通过上下文把时间关系暗示出来。这种时间状语可以表示过去某一时刻正在进行的动作。
eg:
What were you doing yesterday at seven p.m?
When i went downstairs ,they were already eating breakfast.
也可表示过去某一阶段一直在进行的动作。
eg:
From 1983 to 1988,he was teaching at Yale(耶鲁大学）
They were building a dam last winter .
2:表示过去某种习惯性动作
过去进行时所表示的习惯动作通常是指过去某一阶段暂时性的习惯。
eg:
George was getting up at five every day that week .
这句话的含义是，George平时起的没有那么早，只是在那一周当中，他每天5点起床。
过去进行时也可与always,constantly,continually,for ever等状语连用表示感情色彩。
eg:
My brother was always losing his keys.
Alice was constantly changing her clothes.
过去进行时的这种用法，和现在进行时一样，通常表示说话人对某种行为的厌烦等不满情绪。
3：表示过去将来时间里的动作
过去进行时在一定上下文中也可表示按照计划即将发生的过去将来事态。
eg:
They were leaving a few days later.
The summer vacation was drawing near ,but nobody knew where they were gonig for the holiday.
过去进行时用在某些时间状语和条件状语分句中还可表示过去将来时间正在进行的动作。
eg:
He promised not to mention this when he was talking to her.
He told me to wake him up if he was sleeping.
4:表示现在时间和将来时间里的动作
过去进行时的这种用法是为了表示婉转口气以及表示某种臆想的、非真实的情况。
a:表示婉转口气
用过去进行时表示婉转口气只限于hope,want,wonder等动词，主要用来表示有礼貌的请求。
eg:
I was hoping you could send me some books.
I was wondering if you'd like to come out with me .
b:表示主观臆想的情况
过去进行时这一用法仅限于某些固定结构。
eg:
I wish they were not talking so loudly.
I'd rather you were going at once.
Would you stay a little longer,if you were enjoying yourself?
If they were leaving tonight,i'd like to go with them.
It is time we were leaving.
5:过去进行时与一般过去时用法比较
a:表示已经完成的动作用一般过去时，表示未完成的动作用过去进行时
eg:
I was reading a novel yesterday.(未读完）
I read a novel yesterday.(已读完）
They were building a dam last winter.(在建造中）
They built a dam last winter .(建造好了）
b：一般过去时通常只说明过去某时发生某事，而过去进行时则侧重在动作的持续时间，而不仅是说明事实。
eg:
It rained /was raining all night .
He worked /was working all through the night.
在上述两例中，用一般过去时和过去进行时都可以，只是过去进行时更加突出时间持续之久。
c:当一般过去时与过去进行时同时出现在句中时，通常是表示较短的动作用一般过去时，表示较长的动作用过去进行时。
eg:
While I was dictating a letter to my secretary,my wife rang.
I broke a glass while i was cooking the dinner .
I was running downstairs when i slipped and fell.
