Abstract: In order to determine the effective influence radius of the seam air injection, based on the seam gas seepage theory, gas diffusion theory, multi element gas competitive adsorption, energy conservation and ideal gas status equation, taking the seam gas flow filed around the borehole as the study object, a mathematics model of the air injection to remove and replace seam methane was established. Taking the measured parameters of Shigang Mine as the calculation basis, the Comsol software was applied to the numerical simulation on the gas flow equation of the gas drainage borehole under different air injection time and different air injection press ure.The simulation showed that the effective influence radius of the air injection would increase with the air injection time and air injection pressure increased and could provide the basis to the site air injection.