Abstract: In order to evaluate the gas drainage standard effect of hydraulic flushing permeability improvement and pressure relief in floor drainage roadway by crossing borehole, the crossheading floor drainage roadway was taken as test point, which was under 11231 of Baiping Coal Industry Company, it studied the changes of the amount of vent coal from the drilling, gas pre-drainage rate and gas content after hydraulic flushing. The results showed that, the vent coal amount of the evaluation unit was 30‰, gas pre-drainage rate was 31%, and gas content dropped from 7.86 m³/t to 6.10 m³/t after hydraulic flushing. The gas drainage reached standards in the evaluation area, and it eliminated the outburst danger in the excavation process of coal roadway.