Abstract: In order to evaluate the coalbed methane development potential of the gas coal and fat coal in China, the proximate analysis and macerals dataof 81 ga s and fat coal samples were collected from the national scope. The tests were conducted on the porosity, mercury injection and other isothermal adsorption.The results showed that the gas coal and fat coal in China mostly were the ultra low ash coal.The crack development of the gas coal and fat coal at each stage would be balance, t he micropore of the gas coal and fat coal would be best developed and the large pore and the transition pore would be the second.The total specific pore volume and th e porosity would be firstly reduced and then increased with the coal metamorphic degree increased.When 0.65%