一、过去完成进行时：过去完成进行时强调动作从过去的过去开始一直延续到过去某个时间点。在过去某个时间点时，这个动作可能刚刚停止，也可能仍然在进行，由"had been +动词ing"构成。
二、过去完成进行时的用法：
1.表示过去某一时间之前一直进行的动作。过去完成进行时表示动作在过去某一时间之前开始，一直延续到这一过去时间。和过去完成时一样，过去完成进行时也必须以一过去时间为前提。
例如：①I had been looking for it for days before I found it.这东西我找了好多天才找着的。　
②They had only been waiting for the bus a few moments when it came.他们只等了一会儿车就来了。
2.表示反复的动作。
例如：①He had been mentioning your name to me.他过去多次向我提到过你的名字。　
②You had been giving me everything.你对我真是有求必应。
3.常用于间接引语中
例如：①The doctor asked what he had been eating.医生问他吃了什么。
②I asked where they had been staying all those days.我问他们那些天是呆在哪儿的。
4.接具有“突然”之意when句。
例如：①I had only been reading a few minutes when he came in.我刚看了几分钟他就进来了。　　
②She'd only been reviewing her lessons for a short while when her little sister interrupted her.她温习功课才一会儿，她妹妹就打断她了。　
③I had been sleeping when my friend telephoned me.我正在睡觉时，我的朋友给我打电话。