Abstract: Based on anthracite coal as a raw material, one step carbonization-a air phase carbon deposition technique was applied to prepare a carbon molecular s ieve for the coalbed methane purification and to study the carbon deposition time affected to the separation performances of the carbon molecular sieve. The CO2adsor ption ( 273 K) and an electronic balance were applied to the representation of the sample pore structure parameters and gas adsorption capacity individually, to the sep aration performances of the pressure varied adsorption device to the sample CH4/ N2 mixed system and a comparison was conducted with the commercial carbon mole cular sieve. The study results showed that when the carbon deposition time was 60 min, the performances of the carbon molecular sieve prepared would be good and t he economy would be optimum. A0.4 ~ 0.7 nm pore structure would be the main factor affected to the CH4/ N2 resistance effect of the carbon molecular sieve as verif ied and meanwhile a0. 8~ 1.5 nm pore and total pore volume would be the main factor affected to the capacity of the carbon molecular sieve to treat the raw material gas.