Abstract: The North₁ 202 working face of Daxing Coal Mine adopts ultra-long open-off cut arrangement, and there are many factors such as large goaf space, mining of coal seam prone to spontaneous combustion, the whole process downward mining of working face, and large amount of residual coal in goaf of compound coal strata in roof, which greatly increase the difficulty of fire prevention and extinguishing of working face.Through four bundle pipe measuring points embedded in goaf behind the frame at the air inlet and return airway of the working face and 70 m from the upper and lower corners to the working face, the distribution of "three zones" of spontaneous combustion in goaf of North₁202 ultra-long downward working face were observed at multiple-points, it was concluded that the maximum width of oxidation zone in goaf of ultra-long downward working face was 37.7 m, which is located in goaf behind the frame 70 m from the upper corner to the working face.In addition, according to the actual parameters of North₁202 working face, a 3D geometric model was established.Through Fluent simulation analysis, the variation law of goaf flow field and O₂ volume fraction in ultra-long downward mining face was revealed. The simulation results of "three zones" of spontaneous combustion in goaf were compared with the measured results, and it was concluded that the two results were basically consistent.It is proved that the numerical simulation method is effective and scientific to analyze the distribution law of flow field in goaf and O₂ volume fraction in ultra-long downward working face.