Abstract: In order to study the affecting factors for coalbed methane desorption kinetics, desorption kinetics tests were designed under different pressure, temperature, grain size and moisture with anthracite from South Sichuan Coalfield. A self-made HTHP coalbed methane desorption tester was applied in desorption kinetics experiments. Diffusion coefficient was got by fitting result of test. Gas desorption capacity and rate of granular coal increase with increasing adsorption equilibrium pressure and temperature, and decrease with increasing grain size and moisture. The fitting result of diffusion coefficient reveals that diffusion coefficient is increasing with temperature but decreasing with pressure and moisture.