There was a lot of unrecovered coal in the goaf of the 9-301 working face of the Pangpangta Mine. The coal seam spontaneous combustion was likely to occur during the mining of the working face. In order to determine the range of the spontaneous combustion zone in the goaf, CoMSOL Multiphysics were adopted to simulate the porosity and oxygen concentration of the goaf numerically, and the main range of the spontaneous combustion zone in the goaf was 40 ~ 108 m from the stope. Based on this, the nitrogen injection fire prevention technology was used to carry out the goaf at 10 ~ 108 m. After nitrogen injection, the gas concentration was monitored in the goaf. It was found that the main oxygen concentration was stable at about 4%, and the gas concentrations of CO, CO2, CH4, and all showed a rapid decline trend, indicated hat the nitrogen injection prevention in the goaf fire extinguishing technology can effectively suppress the spontaneous combustion of the coal seam in the goaf, thereby ensured the safe mining of the working face.