Abstract: As the depth of underground coal mining continues to increase, the permeability of coal seam further decreases, and the difficulty of coal seam gas extraction also increases.For single unprotected coal seam, most of them need to artificially increase permeability.Hydraulic fracturing has been widely applied due to its wide range of permeability improvement and relatively high cost performance.For low permeability coal seam in deep well, in order to further improve the gas extraction efficiency, the anti-permeability technology of single hydraulic fracturing can not meet the needs.Then, according to the geological conditions of Ji₁₅ 31040 working face of No.12 mine, relevant hydraulic fracturing parameters are designed, and the effects of repeated hydraulic fracturing and gas extraction after fracturing are tested.The results show that after repeated hydraulic fracturing of coal seam, the residual gas content of coal seam decreases more obviously than that of single fracturing, and the gas extraction concentration and scalar also increase significantly.The experimental results show that repeated hydraulic fracturing can significantly improve the gas extraction efficiency of deep well and low permeability coal seam, and has certain application value of gas control.