Abstract: In order to study the diffusion characteristics of granular coal in methane adsorption process, based on the power function diffusion model of adsorbed methane in granular coal and using magnetic suspension balance high pressure isothermal adsorption instrument, the change of diffusion amount with time during the process of adsorption of methane by granular coal under different pressure was determined and the diffusion characteristics of methane adsorbed by granular coal before equilibrium were studied. The result shows:the equilibrium pressure has a significant influence on the adsorption and diffusion characteristics of granular coal, the adsorption capacity and average diffusion coefficient increase with the increase of pressure. In the process of adsorption of methane by granular coal, the diffusion coefficient decays as a power function over time, and decays greatly in the first 500 seconds, and the average diffusion coefficient is negatively correlated with time. Research suggests particle diffusion model for describing particle coal methane adsorption power function of coal methane adsorption diffusion process with high accuracy, will contribute to analyze the dynamic changes of the coalbed methane mining process of coalbed methane adsorption quantity drained, enhancing coalbed methane recovery.