Abstract: In order to evaluate the effect of hydraulic fracturing of coal seam objectively and optimize the layout of extraction borehole, the effective stress value of coal after hydraulic fracturing was corrected based on the principle of statistical damage mechanics, a fluid-solid coupling model was established to describe the process of hydraulic fracturing of coal seam. A two-dimensional fluid-solid coupling model was established to simulate numerically based on the correlative physical parameters in 3309 working face of Sihe Coal Mine. The results show that under the same conditions, with the extension of hydraulic fracturing time, the influence scope of hydraulic frcturing gradually expands, and the permeability of coal seam also presents the same change; with the increase of fracturing time, the porosity of coal seam gradually increases, and finally approaches a fixed value, under this condition, increasing the water injection pressure of coal seam has little influence on the permeability enhanced of coal seam; compared with the origin coal seam, the effective radius of gas extraction in coal seam after hydraulic fracturing greatly increases, and the effect of permeability enhanced is better. The research results can provide theoretical support for the application of hydraulic fracturing technology in situ.