过去进行时表示的是在过去某一时刻或某一段时间内进行或发生的动作，这个动作是延续性的。所以，非延续性动词和表感觉，感情，情绪，精神活动，所属关系等的动词，一般都不用于过去进行时态，常见的这类动词不能用于过去进行时的主要有：agree， be， believe， belong， care， forget， hate， have（拥有）， hear， know， like， love， mean， mind， notice， own， remember， seem， suppose， understand， want， wish等。例如：
误：He is denying that he has seen the wallet.
正：He denies that he has seen the wallet.他否认他曾经见过这个钱包。
误：I was knowing the answer.
正：I knew the answer. 我知道答案。
误：I wasn't understanding him.
正：I didn't understand him. 我不明白他的意思。
误：i was reading when she was coming.
正：i was reading when she came in.她进来的时候，我正在读书。
误：While we were talking, the teacher was coming.
正：While we were talking, the teacher came in. 当我们正在说话的时候，老师进来了。
误：When someone was knocking at the door, we were having supper.
正：When someone knocked at the door, we were having supper.
有人敲门时，我们正在吃晚饭。
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.
A. 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。