I would to know how can i get China visa for 3 to 6 months .

Muhammed, single-entry one is usually valid for 3 months and its duration is just 30 days. However, there are six months multiple ones too. If you plan to apply for the multiple one, you have to provide related document that you really need to apply for it. Otherwise, the consular officers won't give the six months multiple one to you.