1) 概念：表示过去某时正在进行的状态或动作。

2) 过去进行时的主要用法是描述一件事发生的背景;一个长动作发生的时候，另一个短动作发生。

3) 常用的时间状语

this morning, the whole morning, all day yesterday, from nine to ten last evening, when, while

My brother fell while he was riding his bicycle and hurt himself.

It was raining when they left the station.

When I got to the top of the mountain, the sun was shining.

典型例题

1) Mary ___ a dress when she cut her finger.

A. made　 B. is making　 C. was making　 D. makes

答案C. 割伤手指是已发生的事情，应用过去时。同　时，when表时间的同时性，"玛丽在做衣服时"提供事情发生的背景，因此用过去进行时。

2) As she ___ the newspaper, Granny ___ asleep.

read; was falling　B. was reading; fell　C. was reading; was falling　D. read;fell

答案B.句中的as = when, while，意为"当……之时"。描述一件事发生的背景时，用过去进行;一个长动作发生的时候，另一个短动作发生。句意为 "在她看报纸时，奶奶睡着了。"句中的 fell (fall的过去时)，是系动词，后跟形容词，如：fall sick。