I had many times travel to china and now my multiple visa is getting expire

Rambod, you want to apply for multiple-entry business M type entry permit, right? If yes, you can just start over the same process for your last multiple entry M type application to apply for a new one, but I’m afraid you cannot get a 2-year one. Just have a try to apply for a one-year multiple-entry business M type.
You should first prepare the required documents containing your passport and copy of its data page, the application form, a recently-taken passport-style photo, and an invitation from your business partner.
And then submit the application to the embassy of PRC to apply for it and the consular officer will give you a proper M type according to your business trip itinerary.