1)它是用来表示在特定的某一时刻正在发生的事情，或者过去某一时段内持续发生的事情。主要从点和段上来强调动作的过去进行时。

What were you doing at nine last night?

I first met Lisa three years ago. She was working at the radio shop at that time.

2)表示过去某一阶段内一直在进行的动作。

I was reading a novel last night.

As she was reading the newspaper, her sister was doing her homework.

过去进行时在近年高考中的考查:

1. - Sorry to have interrupted you. Please go on.

-- Where was I?

-- You _______you didn't like your father's job. (04 北京)

　A. had said B. said C. were saying D. had been saying

2. - You were out when I dropped in at your house. (04 广东)

-- Oh, I _____ for a friend from England at the airport.

　A. was waiting B. had waited C. am waiting D. have waited

3. - Has Sam finished his homework today?

-- I have no idea. He _____ it this morning. (04吉林)

　A. did B. has done C. was doing D. had done

4. - What's wrong with your coat? (05 重庆)

-- Just now when I wanted to get off the bus, the man next to me ____ on it.

　A. sat B. had sat C. had been sitting D. was sitting

Answers: CACD

4. 一般过去时和过去进行时的区别

1). 一般过去时表示在过去某时发生的动作或存在的状态（包括过去习惯动作），常与just now, a moment ago, yesterday, last week(month, year), the day before yesterday及表示过去的时间状语从句。如

I was sixteen years old last year.

He worked in a factory in 1986.

I met her in the street the day before yesterday.

He often swam in the river when he was young.