过去进行时是排位第五的常用时态，在所有时态的使用统计中占比是0.7%。
用法
1. 表示过去某个时刻或某段时间正在发生的动作或存在的状态，常和过去时间状语连用。例：I was reading a book at four o’clock yesterday afternoon.
2. 在when引导的从句中用一般过去时，主句用过去进行，表示短暂性动作发生的时候，另外一个长时间动作正在进行。例：When the phone rang, I was taking a bath.
3. 表示过去反复发生的动作，常和always, frequently, continually等连用，表达不满等情绪。例：Your father was always doing his work.
4. 在故事中的实际动作发生前，设置一个故事场景。例：He was walking in the park, suddenly a man ran towards him.
结构
1. 肯定句：主语＋was/were+doing+其它。例：I was doing my homework at 5 o’clock yesterday.
2. 否定句：主语+was not/were not+doing+其它。例：I wasn’t doing my homework at 5 o’clock yesterday. 缩略：was not=wasn’t; were not=weren’t.
3. 一般疑问句：Was/Were+主语+doing+其它？肯定回答：Yes, 主语+was/were. 否定回答：No, 主语+wasn’t/weren’t. 例：Were you doing your homework at 5 o’clock yesterday?
4. 特殊疑问句：特殊疑问词+was/were+主语+doing+其它？例：What were you doing at 5 o’clock yesterday?
