Abstract: Based on the upper corner gas content over limit problem of No.14211 fully mechanized top coal caving mining face with gateway retained along goaf in XinDan Mine,a study was conducted on the gas migration law of goaf in the fully mechanized top coal caving mining face . According to the CFD numerical simulation the ory,the 3D inhomogeneity model of goaf gas seepage was established and the determination method of the related parameters was provided for the model.The Fluent n umerical simulation software was applied to compare and analyze the gas migration and gas content distribution law of the goaf under the gas drainage condition availa ble or not at the upper corner of the fully mechanized top coal caving mining face with a gateway retained along goaf.The simulation results showed that the gas draina ge at the upper corner could reduce 42% gas in the upper corner and goaf in average.Thus the gas accumulation problems of the upper corner in the fully mechanized t op coal caving mining face with gateway retained along goaf was effectively solved and the safety production of the fully mechanized top coal caving mining face with g ateway retained along goad could be protected.