Abstract: For the technical problems of poor gas extraction effect in low permeability and soft coal seam, the paper studies the high efficiency gas extraction technology by long multi-point directional drilling hydraulic fracturing, and discusses the mechanism of hydraulic fracturing and permeability improvement in low-permeability weak coal seam. On the basis of constructing the long multi-point directional drilling and the quick hole sealing equipment of underground hydraulic fracturing, the field test of hydraulic fracturing in underground coal mine is carried out. This paper analyzes the laws of parameter variation during fracturing, and proposes the influence range of hydraulic fracturing, fracturing effect and the evaluation method of gas extraction, and carries out the effect investigation. The results show that this technology improves the hole sealing efficiency and construction quality of underground hydraulic fracturing, improves the parameters of coal reservoir in the test area, the water content increased by 4.31 times, and the permeability increased by 4.88 times; the influence range of hydraulic fracturing is 50 m to 60 m along the radial of borehole; the maximum impact range along the axial direction is about 40 m. Continuously extracting 233 d after the fracturing, and the cumulative gas extraction is 25.14 × 104 m³, the daily maximum extraction amount is 3 077.41 m³/d, and the gas content decreased by 34.67%.