I know you are a student good at math.是什么结构.

I know you are a student good at math.
=I know you are a student (who is) good at math.
I 主语 know 谓语动词,you are a student (who is) good at math.整个是宾语从句.
这个宾语从句中,又有个定语从句,先行词为a student,关系代词who.