I am interested in doing medicine although i have graduated with a Diploma of Commerce,,Is it possible?

I think it will be hard for you to do medicine.
Most Chinese colleges have their requirements on the candidates. If you want apply for such kind of degree, you may have relative thesis and you have to pass a certain exam held by the school.
I think you can find more detail information on the official website of some universities. There are some listed for you for reference: Peking University, Zhonshan University and Fudan Univerisity.