Abstract: In order to further improve the antireflection effect of hydraulic fracturing of deep low permeability coal seams, based on the theories and field studies related to the hydraulic fracturing technology of coal seam, according to the relevant mechanical principles, the variation of the stress around the fracturing hole with the flow rate of water injection was deduced. Based on the principle of controlling the injection water flow, a method of unstable injection water flow in the process of hydraulic fracturing was proposed.The hydraulic fracturing test was carried out in the Ji₁₅-31040 working face of No.12 Coal Mine in Pingdingshan Coal Industry Group. The test results show that the influence of high in-situ stress in deep coal seam on hydraulic fracturing is overcome by injecting unstable water flow, and the roof is maintained in good condition during fracturing; after measuring the gas extraction data of conventional stable water flow fracturing and unfractured area of Ji₁₅-31030 working face adjacent to Ji₁₅-31040 working face, it is found that the concentration and pure flow of gas extracted from single hole in unstable water flow fracturing are significantly increased.This method has a certain guidance for the antireflection of deep coal seam hydraulic fracturing.