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To study the variation of the pressure relief scope and the stress around hydraulic flushing borehole, the theory of coalrock damage was utilized to distinguish the interaction area of water-jet and coal-rock into the coal-rock crushing area, the water-jet pressure stagnation area, the transition area and the original stress recovery area of coal-rock. Based on the actual occurrence conditions of the coal seam, the pressure variation and relief scope around the hydraulic flushing borehole were analyzed and simulated by RFPA2D-Flow software. The results showed that a relief area with the radius of 5.0 ~ 6.0 m around the borehole formed due to the hydraulic flushing with the pressure relief of 0.038 ~ 6.545 MPa, and the maximum principal stress is 15.85 MPa with a distance of 6.8 m from the inspected hole where stress concentration appeared. After hydraulic flushing test, the diameter (441.8 ~ 1171.6 mm) of the hole which can be an expression of coal crushing area size, was calculated based on the examination of the coal amount through the trial process, and it can be drawn that the pressure relief area must be larger than that of the coal-rock crushing area. Meanwhile, the measured pressures relief range(5.96 ~ 6.62 m) is basically consistent with the numerical simulation result (5.0 ~ 6.0 m) which verified the accuracy of the simulation analysis, according to the distance from the inspection drilling to the hydraulic flushing borehole and the decreased degree of the gas content in the inspection hole by the way of Gas Content.