Abstract: Aiming at the problem of over-limit gas in the return air corner of the “U” type downward ventilation fully mechanized caving face in Baode Coal Mine, the law of gas migration in the stope and goaf was studied. Using Fluent numerical simulation software and using the 81308 fully mechanized caving face as a model, the gas migration and gas concentration distribution in the goaf and the return air corner are numerically simulated according to different mining parameters in the goaf. The simulation results show that based on the mining conditions of the 81308 fully mechanized caving face, the gas drainage spacing and the drainage volume in the goaf of the working face are respectively 90-120 m and 600 m3/min. According to the simulation results, engineering practice was carried out during the mining in the 81308 fully mechanized top-coal caving face to determine the reasonable goaf gas drainage parameters of the working face and effectively solve the “U” type downward ventilation, high-yield and high-efficiency fully mechanized caving face return air.