In order to obtain the gas distribution in the goaf of the spontaneous combustion coal seam and the law of the disaster caused by the superposition, the gas concentration and temperature distribution in the goaf of the 50,221 working face were sampled and observed by the field beam tube, and the variation law of the gas and temperature distribution was obtained. According to the gas explosion range and the spontaneous combustion zone division standard, the gas concentration explosion interval and the oxidation zone range in the goaf were determined. The Fluent software was used to numerically simulate the gas and oxygen migration law in the mined area. According to the simulation results, the movement of the air leakage fluid and the gas concentration are analyzed. The results show that the air leakage on the intake side of the working face is large, and the spontaneous combustion zone is the widest, with a width of up to 46 m. The gas in the upper part of the coal mining face and the return airway on the return air side exceeds the limit seriously, and there is an overlapping dangerous area of gas fire area in the goaf.