In view of the problem that H2S is difficult to control in coal mines, a three-dimensional model of No. 13 coal seam in Shaping Coal Industry was established by numerical simulation software COMSOL Mutiphysics. The numerical simulation of coal seam alkali injection was carried out to analyze the reaction law of alkali solution (Na2CO3 ) and H2S under different pressures and pore numbers. The results show that the influence range of alkali injection increases with the increase of time in single hole alkali injection, and the diffusion range of alkali solution increases with the increase of alkali injection pressure in double hole alkali injection. Under the pressure of 4 MPa, alkali injection for 48 h, single hole alkali injection up to 6.4 m, double hole alkali injection up to 9.8 m. In the field application of No. 13 coal seam, the porous alkali injection method is used in the field. The pore spacing of the coal seam is 8 m and the alkali injection pressure is 4 MPa, which proves that the simulation results have remarkable effects on practical application.