Abstract: Aiming at the difficulty of pre-drainage gas in low permeability and high gas coal seam, the technology of directional hydraulic fracturing of coal seam with guide groove is proposed. The distribution of plastic zone after reaming in coal seam is calculated by theoretical derivation, and the initiation and propagation of hydraulic fractures in coal seam of cross-seam drilling are analyzed to reveal the mechanical mechanism of directional hydraulic fracturing of coal seam with guide groove. The permeability-increasing equipment for directional hydraulic fracturing of coal seam with guide groove was developed and applied in Shanxi Zhongxing Coal Mine. The results show that after the water jet method is used to expand the coal seam section of the cross-layer borehole, an approximately cylindrical hole is generated in the coal body. The radius of the plastic zone of the surrounding rock of the cross-layer borehole is positively related to the radius of the borehole. Drilling reaming is an effective method to increase the range of the plastic zone, which has a significant role in promoting the development of cracks, thereby improving the gas extraction effect. A complete set of equipment for directional hydraulic fracturing and outburst prevention of guide groove is developed. The main components are mobile high-pressure hydraulic pumping station, nozzle, nozzle, orifice blowout preventer, spiral assisted slag discharge water jet high-pressure drill pipe and high-pressure rotary joint, combined with remote monitoring and control of downhole hydraulic operation. The field monitoring results show that the average gas concentration and the mixing amount of gas drainage are increased to 2.75 times and 1.81 times of that of the conventional hole by the method of permeability-increasing drilling, which indicates that the permeability-increasing effect of directional hydraulic fracturing with guide groove is remarkable. The research results provide a new technical approach for pre-drainage gas in low permeability and high gas coal seam.