busy doing和busy to do的含義不同、用法不同。be busy doing sth其實也可以是be busy (in) doing sth.意為忙于做某事；be busy to do sth.一般是be too busy to do sth.意為太忙了以至于不能干什么。

People are always out in their cars,watching television or busy doing something else.

人們總是駕車外出，或者看電視，再不就是忙點其他什么事情。

I am busy doing my homework right now.

我現(xiàn)在正忙著在做課外作業(yè)。

Was it because you were too busy doing everything else?

是因為你有很多別的事情要忙著做嗎？做了很多事，意味著你很忙。

Because I was busy doing something else.

我在處理別的事。

I'm busy doing that today.

我今天在忙著做那件事情。