Which sentence wrong?
Who rides his bike?
Who does ride his bike?

and tell me the reason ! plz. thank you!

Question

Which sentence wrong?
Who rides his bike? 
Who does ride his bike?
 
and tell me the reason ! plz. thank you!

Answer

Sometimes we use do/does to give more emphasis to the sentence. 
Both sentences are correct.
Other examples are
-I wash the dishes.
-I do was the dishes.

-I did my homework.
-I did do my homework.

Answer

must be "Which sentence is wrong?"... this one is wrong =>Who does ride his bike?