"Have done" is the present perfect, and is used to show something has happened in the past that continues until, or affects, the present. For example: "I have done my homework" (it is finished) or "I have done some bad things in my life" (and I may do some more bad things before I die). "Had done" talks about what happened before something else happened: e.g., "He had done his homework before he went to school" (both are in the past, and this shows a sequence of events) or "He had done many bad things in his life before he died, but he apologized to those he had hurt in his final hours."

have done 到目前为止已经完成 had done 以前就已经完成。

There's quite a lot of difference. You know, when you ask such general questions like this it is very difficult to make a satisfactory answer. have done = 现在完成时 had done = 过去完成时

Here's how to use them. Have done = something happened in the past, and it is significant to the moment right now. I have done it, so stop asking... he has done it, so I don't need to do anything... you have done it, I am happy for you. Had done = what most people miss is that a past perfect phrase cannot exist alone. It needs another event to come after it (see Brad C's answer). We use past perfect to put events in order, without needing to say them in the order which they happened. The past perfect automatically places that event *first*. Which is great if you want to hide a piece of information until later. "I have done the final tests for curing cancer! My older brother had done the same." (=my brother cured cancer first! Curses!!)

Kevin, your question is way too general. Most students spend HOURS studying the two phrases you have asked about here.