型態
在第三類條件句中，會用到完成進行條件式。
| if 子句（條件/情況） | 主要子句（結果） |
|---|---|
| if + 過去完成式 | 完成進行條件式 |
| If this thing had happened | that thing would have been happening. |
作用
完成進行式可以用在第三類條件句，論及 if 子句中的動作未達成的後果，並將這樣的後果以未完成或持續進行的動作來表達。
舉例
- If the weather had been better（但沒有）, I'd have been sitting in the garden when he arrived（但我沒有）.
- If she hadn't got a job in London（但她有）, she would have been working in Paris（但她沒有）.
- If I had had a ball I would have been playing football.
- If I had known it was dangerous I wouldn't have been climbing that cliff.
完成進行條件式
任何動作的完成進行條件式都是由四個要素組成：
would + have + been + 現在分詞
現在分詞的構成是取動詞的原型，並在字尾加上 ing。
| 主詞 | + would | + have | + been | + 現在分詞 |
|---|---|---|---|---|
| He | would | have | been | staying |
| They | would | have | been | going |
完成進行條件式，以 To Work 為例：
| 肯定句 | 否定句 | 疑問句 | 否定疑問句 |
|---|---|---|---|
| I would have been living | I wouldn't have been living | Would I have been living? | Wouldn't I have been living? |
| You would have been living | You wouldn't have been living | Would you have been living? | Wouldn't you have been living? |
| He would have been living | He wouldn't have been living | Would he have been living? | Wouldn't he have been living? |
| She would have been living | She wouldn't have been living | Would she have been living? | Wouldn't she have been living? |
| We would have been living | We wouldn't have been living | Would we have been living? | Wouldn't we have been living? |
| They would have been living | They wouldn't have been living | Would they have been living? | Wouldn't they have been living? |