一、过去将来完成式：过去将来完成时表示从过去观点看将来某时某动作已完成。
二、过去将来完成式的用法：表示从过去某一时间来看将来某时会已经完成的动作。
例如：①I thought Sophia would have told you something.我想索菲娅会已告诉你一些情况。
②He knew by the time he arrived she would have gone home.在他到时他才知道她已经回家了。
③The day was drawing near when we would have completed the reservoir.我们建成水库的日子不远了。
④He 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。
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”。
例如：①If 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)
②If 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)
③If I had known that you were coming I would have met you at the airport.要是我早知道你要来的话，我就会在机场接你了。
三、“would + have + 过去分词”的情态用法：
would 后接完成式除用于构成过去将来完成时外，它还有其情态动词用法的一面。
例如：①Only somebody with a small mind would haverefused to help.只有心胸狭窄的人才不肯帮助别人。（表推测）
②Few men would have bared their soul to a woman as he had.很少有男人能像他一样对一个女人敞开心扉。（表怀疑）
③I'm surprised you didn't like the film. I would have thought it was just your kind of thing.你不喜欢这部电影，这让我感到奇怪。我本来还觉得正对你的路呢。（表过去的想法）
④My father would have driven me to Cornwall, but we decided it would be quicker by train.父亲原本要开车送我去康沃尔，但我们还是觉得坐火车更快。（表过去的想法）
⑤The scar added interest to a face that otherwise would have appeared too bland.这处伤疤为本显得平淡无奇的脸增添了些吸引力。（表示未曾发生的情况）