In order to get coal seam stress and water injection pressure in fracturing stage law, the on-site reduction fracturing process was conducted in the laboratory by similar materials, the changing law of injection pressure, seam stress and seam crack expansion. The test showed that the increase of water injection pressure and the speed of coal fracture were affected by the ground stress, the greater ground stress, the slower the increase of water injection pressure and the speed of coal fracture, 75 mm away from the water injection hole was the pressure relief range of the hydraulic fracturing test for drilling. The stress of coal body transfers to the depth after water injection, the fracture begins to extend with hydraulic pressure fracture as the center, fracture development in pressure relief range can be divided into three grades, cracks within 40 mm were the largest, followed by cracks between 40 and 60 mm, and cracks between 65 and 80 mm the smallest. After adjusting the fracturing scheme of water injection hole, the gas concentration was 20% higher than that of conventional fracturing; Drilling and extraction flow rate was 40% higher than conventional fracturing, after adjusting the fracturing scheme of water injection hole, the gas concentration was 20% higher than that of conventional fracturing; drilling and extraction flow rate 40% higher than conventional fracturing.