I am interested to study china language diploma in china. what i do for that?

You should select a favorite Chinese school and apply for the admission of the school. Then apply for a China student visa with the Foreign Student Visa Application Form (JW201 or JW202) issued by the Chinese authorized unit, the Admission Notice from the Chinese school, a ful-filled China visa applicatin form, your valid passport and a recent-taken passport-size photo. Finally, you can go to China for the study.