I like a girl in school, but she hate me what should I do

You should talk to her directly. Introduce yourself and ask if you could make friend with her. If she ignore you again, that means she don't even want to know you. Although the girl is pretty, a bad personality is not attractive.

Do you kown why do she hate you ?
Find the 原因 and corret
Make she love you
If you can't ,forget her la

Forget her, you should spent more time in study than thinking of a girl. You are still young, if study hard, have good school results, good jobs, you have much better chance to know even better, prettier girls. Don't be a fool.