型態
未來完成進行式是以兩個要素組成：
Be 動詞的未來完成式 (will have been) + 主要動詞的現在分詞（動詞原型 + ing）
| 主詞 | + will have been | + 現在分詞 |
|---|---|---|
| He | will have been | playing. |
| I | will have been | playing. |
未來完成進行式，以 to live 為例
| 肯定句 | 否定句 | 疑問句 | 否定疑問句 |
|---|---|---|---|
| I will have been living | I won't have been living | Will I have been living? | Won't I have been living? |
| You will have been living | You won't have been living | Will you have been living? | Won't you have been living? |
| He will have been living | He won't have been living | Will he have been living? | Won't he have been living? |
| We will have been living | We won't have been living | Will we have been living? | Won't we have been living? |
| They will have been living | They won't have been living | Will they have been living? | Won't they have been living? |
作用
就如未來完成式，此時態表達對未來的期待，並反觀未來某時間會完成的事。它涉及現在和未來之間未完成的持續性動作。通常會與時間詞一起使用。
舉例
- I will have been waiting here for three hours by six o'clock.
- By 2001 I will have been living in London for sixteen years.
- When I finish this course, I will have been learning English for twenty years.
- Next year I will have been working here for four years.
- When I come at 6:00, will you have been practicing long?