Abstract: In order to improve the extraction efficiency of low permeability and hard pumping coal seam, the technology and equipment of small curvature bend drill based on water jet applied for the drilling of comb holes was studied, the structure of hydraulic perforating self-propelled drill nozzle was studied and optimized. Based on the combination of water jet and segmented fracturing, drilling, pressing and pumping three in one coal seam gas permeability improving technology system and process flow for hard pumping coal seam was established. And in situ tests in Xinjing mine, field monitoring analysis show that small curvature bend drill combined segmented fracturing technology can fully improve the coal seam gas flow field effectively and significantly improve the efficiency of coal seam gas extraction.