Abstract: This study focuses on the determination and division of the natural fire zones in the goaf of the 5-302 fully mechanized mining face of the steeply inclined 5th Upper coal seam in North Shanxi during the actual mining process. Temperature sensors and tubes were installed in the goaf to monitor the temperature and gas concentration changes during the normal mining phase. Using numerical simulation software, a flow field model of the goaf in the steeply inclined working face was constructed, and simulation data of oxygen concentration fields under different airflows were obtained. Therefore, by combining field experiments with simulation data, the "three zones" of spontaneous combustion in the goaf were successfully divided: the cooling zone near the intake airway has a width of 0-24.0 m, the oxidation zone extends from 22.4 m to 72.0 m, and the asphyxiation zone is located beyond 72.0 m at the working face; the cooling zone near the return airway is 22.4 m wide, the oxidation zone extends from 22.4 m to 67.2 m, and the asphyxiation zone is located beyond 67.2 m at the working face. The minimum advancement speed of the working face is 0.62 m/d. This study provides important guidance for the prevention and control of fires in the 5-302 steeply inclined coal seam.