what should i prepare about Multiple Entries in 6 month? is it hard to apply? I am a canadian and have been China 6 times in the past 2 years.

It is not hard for you to get a multiple entry visa valid for 6 months from application because you have been China 6 times in the past 2 years.

You just need to prove your passport, one passport photo, the filled visa application form V.2011A, the copy of your previous China visas.