Abstract: To investigate the gas migration law in the goaf before and after the pre-splitting and weakening of the mining-induced overburden roof during the extraction of the 9# coal seam in a mine in Inner Mongolia, a three-dimensional geological numerical model of the goaf was established using COMSOL Multiphysics based on the simulated fracture zone development before and after roof pre-splitting. The distribution patterns of gas accumulation zones were simulated and analyzed under different working face advance distances (80 m, 120 m, 200 m, 250 m), different air intake volumes, and before and after the pre-splitting and weakening of the mining overburden roof. The results show that as the working face advances continuously, gas in the goaf displays obvious accumulation characteristics, with the concentration exhibiting a gradient-increasing trend along the strike direction and eventually reaching a stable equilibrium state. After roof fracturing is implemented, the gas concentration within the fracture zone increases significantly, and the extent of the high-concentration gas region in the deep goaf on the return airway side is reduced, effectively improving the conditions for borehole drainage. The research results can provide a theoretical basis for the optimization of pressure-relief gas drainage technology.