Abstract: The main roadway in the 2502 mining area of Yanbei Coal Mine is an isolated island coal pillar with high stress concentration. Due to the thick thickness of the coal seam, large diameter drilling for pressure relief cannot achieve good anti erosion effect. To address this issue, a technical method for hydraulic expansion and pressure relief in coal seams has been proposed. Through theoretical analysis, the pressure relief mechanism of water jet coal breaking and hole expansion was studied, and the main technical parameters of hydraulic hole expansion were determined. The pressure relief mode of segmented hole expansion in the borehole was analyzed using numerical simulation, and corresponding supporting equipment was developed and on-site tests were conducted. Through research, it has been found that hydraulic expansion expands the pressure relief range of a single hole by increasing the drilling diameter. The use of double-layer high-pressure drill pipes can achieve integrated pressure relief of coal drilling and cutting, improving pressure relief efficiency. The on-site test results show that when the water pressure of coal seam hydraulic expansion is 40MPa and different nozzle combinations are used, the expansion radius can reach 0.35m~0.5m, and the amount of drilling debris in the expansion area is significantly reduced. The results indicate that hydraulic expansion can significantly reduce stress concentration in the coal body, achieving the goal of preventing and controlling rock burst.