In order to accurately determine the effective coal seam drill a radius and in order to a reasonable decorate the coal seam the pumping drilling,this paper establishes the drilling of coal around the flow of gas model,and uses COMSOL Multiphysics software solution of the analytical solution of the model.Through the simulation,we get the corresponding solution extraction conditions and the smoke time,drilling extraction effective radius,for extraction of drilling decorate to provide the theory basis,so as to achieve the optimal design,the smallest quantity and the best extraction effect.The test results show that in the practical engineering application,and on the basis of simulation,the gas pressure distribution can identify effective drainage radius with the change of time extraction relationship.This method can overcome the disadvantage of traditional approach,in which there are some shortcomings,as difficult to sealing,and trivial test process.It is simple and accurate to determine the radius of extraction,to provide a theoretical basis for the engineering practice.