Abstract: Based on the dual-porosity characteristics of coal seams,Fick's First Law for Diffusion and the permeability model considering the effective stress impact was included to investigate the impact of the diffusion coefficient on coalbed methane recovery.The evolution of gas output was analyzed in two different scenarios with different diffusion coefficients(1.2×10^-10 m²/s and 1.2×10^-13 m²/s).The results showed that the gas recovery process dominated by diffusion was much longer than that dominated by the gas in free phase.The time scale for the evolution of matrix gas pressure(10⁹s)was two magnitudes larger than that of fracture gas pressure(10⁷s).The diffusion coefficient has unobvious influence on the gas recovery in the initial stage,but the difference developed with the recovery process and reached 3 magnitudes finally.