Aiming at the technical problem of low gas drainage efficiency in soft, fractured and low-permeability coal seam, this study takes the directional long hole hydraulic fracturing technology as the core, and combined with theoretical analysis and field practice, systematically discusses the mechanism of increasing permeability and eliminating outburst and the engineering application effect of hydraulic fracturing in soft and low-permeability coal seam. The research reveals the three-stage characteristics of hydraulic fracture propagation (compaction, initiation and propagation), and defines the dominant characteristics of plastic deformation of soft coal seam and its complex influence on fracture morphology. Through the engineering practice of No.3 Coal Seam in Xinjing company, the scientificity of hydraulic fracturing parameter design is verified. The field monitoring data show that the water injection pressure fluctuates in a zigzag manner during the hydraulic fracturing process, reflecting the dynamic process of fracture “closure opening expansion”, and the maximum influence range is 58 M. after fracturing, the permeability coefficient of coal seam increases by 2.67 times, and the attenuation coefficient of borehole gas flow decreases by 2.22 times, significantly improving the gas drainage efficiency. The research confirmed that the hydraulic fracturing technology can effectively reduce the risk of coal and gas outburst by enhancing the permeability of coal seam, expanding the drainage radius and optimizing the distribution of stress field, which provides a theoretical basis and engineering practice example for the gas control of soft and low permeability coal seam.