Abstract: In order to study the broken scope of coal seam drilling in the process of static blasting and determine the reasonable borehole spacing of gas drainage, by the reaction parameters of the broken material measured by design experiment, and according to the basic parameters and the mathematical model of the coal deformation, we use COMSOL software to carry out numerical simulation for the broken scope of coal seam drilling. Research results show that the inflation pressure caused by the broken material can reach to 45 MPa to 65 MPa; when pore diameter is 100 mm, the radius of crack reach to 1.3 m, and the reasonable drainage borehole spacing are determined.