Abstract: In order to solve the adverse effects for gas extraction due to high geo-stress fractured soft coal seam, a new method of cutting-for-carving to coal seams by high pressure water jet has been proposed, with a view to solving the problem of gas limiting mine production capacity.The installation and process of the high-pressure water jet cutting-for-carving system were tested on site to determine the reliability of the permeability-enhancing technology through a comparative analysis of gas pre-extraction indicators.The extraction effect of ordinary borehole without hydraulic perforation was compared with that of perforation caving pressure relief borehole.The gas extraction concentration and extraction purity flow of the perforation caving borehole are 1.4 times and 6 times respectively of ordinary holes without hydraulic caving, and the hydraulic cutting-for-carving borehole has a clear advantage in the extraction effect.