區別是：
be doing sth就是現在進行時，表示正在做某事。
doing sth 是現在分詞，表示動作主動發生。
例句辨析：
be doing sth
1、He is doing very well in his work.
他在工作中表現很好。
2、Let"s give him line enough and find out what he is doing.
我們對他來個欲擒故縱，看看他還要幹些什麼。
3、The zoo is doing major conservation work, both in captivity and in the field.
無論在圈養場還是在野外，動物園在動物保護方面都承擔了主要的工作。
doing sth
1、I was with fine people doing a good job
我和高尚的人們一起幹著一份不錯的工作。
2、All right, who are you and what are you doing in my office?
喂，你是誰，在我的辦公室做什麼？
3、You let me down doing a thing like that.
你做那樣的事使我太失望了。
區別是：
be doing sth就是現在進行時，表示正在做某事。
doing sth 是現在分詞，表示動作主動發生。
例句辨析：
be doing sth
1、He is doing very well in his work.
他在工作中表現很好。
2、Let"s give him line enough and find out what he is doing.
我們對他來個欲擒故縱，看看他還要幹些什麼。
3、The zoo is doing major conservation work, both in captivity and in the field.
無論在圈養場還是在野外，動物園在動物保護方面都承擔了主要的工作。
doing sth
1、I was with fine people doing a good job
我和高尚的人們一起幹著一份不錯的工作。
2、All right, who are you and what are you doing in my office?
喂，你是誰，在我的辦公室做什麼？
3、You let me down doing a thing like that.
你做那樣的事使我太失望了。