Abstract: In this paper, the combination of numerical simulation and field engineering test is used to systematically study the effect of hydraulic fracturing technology on bottom drainage roadway in the coal seam. In the process of hydraulic fracturing, the law of fracture development, the redistribution of stress and the change of permeability coefficient are obtained, the range of permeability improving in coal seam is obtained, and engineering tests are used to verify the results of numerical simulation. The numerical simulation results are applied in engineering practice, high efficiency extraction of coal seam gas is realized. In the first month after fracturing, the average gas drainage of the single hole is more than 3.6 times of the non-fracturing zone, the pumping time is shortened by more than 40%, all these realize the long time permeability improving and the gas efficient extraction of the coal seam.