1. 构成
was / were+动词的现在分词。
2. 基本用法
(1) 表示过去某一时间点或一段时间正在进行的动作。如：
What were you doing this time yesterday? 你昨天这个时候在干什么？
Granny fell asleep when she was reading. 奶奶看书时睡着了。
He was writing a book about grammar last year, but I don’t know whether he has finished it.他去年在写一本语法方面的书，但我不知道他现在是否写完了。
What were you talking about just now? 你们刚才在谈什么？
He was working from 7 to 11 last night. 昨晚他从七点一直工作到十一点。
(2) 过去进行时与 always, forever, continually等副词连用，表示满意、称赞、惊讶、厌恶等表示感情色彩。如：
My brother was always losing his keys. 我哥哥老是丢钥匙。
The boy was continually asking the same question. 这个男孩子老是问同一个问题。
(3)动词wonder, hope, think, want等的过去进行时表示语气委婉、客气。如：
We were wondering if you would stay with us for lunch. 我不知你能否留下来和我们一起吃午饭。
I was hoping you give me a chance to try the job. 我很希望你给我一个机会来试一试这个工作。
(4)过去进行时表将来。如：
―What were you doing when he came to see you?
―I had just finished my homework and was leaving to
He said his brother was leaving for
3. 过去进行时和一般过去时的区别
(1) 过去进行时通常表示一个过去正在进行的动作；而一般过去时则通常表示一个过去已经完成的动作。如：
I was reading the newspaper last night. 我昨晚在看书。(不一定看完)
I read the newspaper last night. 我昨晚看了报纸。(已经看完)
He was building a model ship out of wood. 他在那里修一座桥。(不一定建成)
He built a model ship out of wood. 他用木头造了个模型船。(已建成)
(2) 少数动词如rain, snow, cough, wear, feel, work等的一般过去时并不表示动作完成，这时用两种时态都可以，且含义区别不大。如：
It snowed / was snowing all day yesterday. 昨天下了一天的雪。
She didn’t feel / wasn’t feeling well that day. 那天她感到不太舒服。
The child coughed / was coughing all night. 这孩子咳嗽了一整夜。