Abstract: In order to improve the gas drainage efficiency of the mining seam in Hongling Mine of Yubei Coalfield and to ensure the safety production and successful r eplacement of the mine,according to the seam deposition law and gas geological condition of the mine,a hydraulic reaming technology of the mining seam was provided,a hydraulic reaming system of the mining seam was established,the related test equipment was optimized, the rational technical process and technical parameters were deter mined and the test effect investigation was conducted. The site industrial test results showed that the attenuation coefficient of the gas flow from the gas drainage borehole within the reaming influence scope was reduced obviously and the month gas drainage volume from the borehole was 2. 17 times higher than the conventional drainage bo rehole. The hydraulic reaming technology of the mining seam could make the borehole gas drainage action area increased,could make the pressure releasing and permeab ility improving of the seam within certain scope of the borehole surrounding area and increase the gas drainage influence radius of borehole ,effectively improve the gas dra inage effect of the borehole,reduce the borehole construction value along the mining seam and reduce the target time of gas drainage.