一、过去将来完成时
过去将来完成时表示从过去观点看将来某时某动作会业已完成。这个时态用得相对比较少，通常主要用于转述方面，即用于间接引语中。如：
The party would have arrived by four o’clock. 这一行人将于4时前到达。
She said she’d have finished her exams by then. 她说那时她会已经考完试了。

二、构成方法过去将来完成时
过去将来完成时由“would+have+过去分词”构成：should / would+ have done sth.

三、基本用法
过去将来完成时的基本用法就是：表示从过去某一时间来看将来某时会已经完成的动作。如：
He knew by the time he arrived she would have gone home. 他知道他到时她会已经回家。
I thought Sophia would have told you something. 我想索菲娅会已告诉你一地情况。
The day was drawing near when we would have completed the reservoir. 我们建成水库的日子不远了。
He said he would have done with my camera by the end of next month. 他说到下月底就不用我的照相机了。

四、过去完成时用于虚拟语气中
若表示与过去事实相反的虚拟语气，此时条件从句的谓语用过去完成时(had+过去分词)，而主句谓语则通常用过去完成时（would+have+过去分词），当然，主句谓语也可根据情况使用“should (could, might)+have+过去分词”。如：
If I'd left sooner, I'd have been on time. 要是我早点动身，我就准时到了。(但我动身太迟了)
If we had found him earlier we could have saved his life. 要是我们当时早点找到他的话，我们就可以救活他。(可惜我们找到他太晚了)