型态
将来完成进行时是以两个要素组成：
Be 动词的将来完成时 (will have been) + 主要动词的现在分词（动词原型 + ing）
| 主词 | + will have been | + 现在分词 |
|---|---|---|
| He | will have been | playing. |
| I | will have been | playing. |
将来完成进行时，以 to live 为例
| 肯定句 | 否定句 | 疑问句 | 否定疑问句 |
|---|---|---|---|
| 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
就如将来完成时，此时态表达对未来的期待，并反观未来某时间会完成的事。它涉及现在和未来之间未完成的持续性动作。通常会与时间词一起使用。
举例
- 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?