過去進行式意指某動作在過去某段時間內「正在進行」，而且持續一段時間才結束。例如：昨天早上七點的時候，我正在吃早餐，就是描述吃早餐這個動作在過去持續了一段時間。
過去進行式的公式
過去進行式＝主詞（人/事/物）＋ was / were + V-ing
a. 肯定句型
I was dancing in the room.
我那時正在房間裡跳舞。
He was running in the park.
他那時正在公園裡跑步。
We were having a picnic.
我們那時正在野餐。
b. 否定句型
I was not dancing in the room.
＝ I wasn’t dancing in the room
我那時沒有在房間裡跳舞。
He was not running in the park.
= He wasn’t running in the park.
他那時沒有在公園裡跑步。
We were having a picnic.
＝ We weren’t having a picnic.
我們那時沒有在野餐。
c. 疑問句型
Was I dancing in the room?
我那時正在房間裡跳舞嗎？
Was he running in the park?
他那時正在公園裡跑步嗎？
Were we having a picnic?
我們那時正野餐嗎？
d. 搭配when / while用法
過去進行式最常見的用法，就是搭配 when 和 while 連接在過去同時發生的兩件事。
I was reading a book when Mom was cooking lunch.
I was reading a book while Mom was cooking lunch.
我那時在讀書的時候，媽媽正在煮午餐。
e. 當when / while在句首
若你看到when / while在句首時，記得用「逗號」把兩個句子隔開喔！
When I was reading a book, Mom was cooking lunch.
While I was reading a book, Mom was cooking lunch.
我那時在讀書的時候，媽媽正在煮午餐。
f. 過去簡單式過去進行式when / while合併例句
在過去某個長時間動作進行的期間，發生了另一件事，這時when和while 的用法不太一樣，我們來看看例句吧！
Mom called when I was reading a book.
Mom called while I was reading a book.
媽媽那時打斷話來的時候，我正在讀書。
搞懂過去進行式後，來點稍稍困難的「現在完成進行式」，別擔心，帶入公式很簡單的！