Abstract: Relying on the gas desorption law experimental system for coal containing gas which was designed and produced by ourselves, by taking coal gas desorption kinetics law as the theoretical basis, it used the method by combination of the simulation test and the theoretical analysis, made analog determination for the gas desorption laws of coal samples with different particle size under isothermal-isobaric conditions. Through making fitting analysis for the experimental data, it obtained the effects of particle size on coal gas desorption laws. Finally, it made theoretical analysis for the effects of particle size on coal gas desorption laws.