星期六你做什么
what do you do on saturdays这是一个一般现在时的特殊疑问句。特殊疑问词what（what， where， who， when， which， whose，等）＋一般疑问句
what在句子中充当宾语成分。you是主语，第一个do是助动词，第二个do是谓语动词，on Saturday是时间状语。也就是You do what on Saturday.
相关句子：
1、 What is your name?
2、Why did you do that?
3、 Where is Michelle?
4、 How does your father go to work?
