In order to solve problems of low gas permeability of coal seam, small gas drainage radius and long drainage time, the technology of coal seam high pressure water injection fracturing was used in 2217 floor rock roadway. Two experiments were carried out with water injection pressure of 25 MPa and 30 MPa respectively. And  influence radius of water injection, the drainage radius and drainage effect before and after water injection were analyzed. The experimental results showed that: the injection radius reached to 15 m and 18 m respectively with water injection pressure of 25 MPa and 30 MPa. The permeability of coal seam was greatly improved after water injection, and gas drainage radius increased from 4m originally to 10m after high pressure water injection fracturing. The single span gas extraction scalar was increased to 0.05～0.135 m3/min after high pressure water injection fracturing from below 0.05 m3/min before high pressure water injection fracturing, which was 1.4 ~ 3.9 times higher than before, and greatly shortened coal seam gas drainage time, providing technical support for mine safety and efficient production.