Abstract: Taking Wulan Coal Mine II020803 working face as the background, the theoretical analysis, theoretical analysis, numerical simulation and field measurement were used to study the effect of gas extraction on nitrogen injection in close goaf of coal seam. The results show that during the oxidation process of residual coal, the distribution of oxygen concentration in the goaf is uneven, and oxygen will diffuse from the high concentration area to the low concentration area. In the normal working face mining process, it can be considered that the gas diffusion and heat transfer process in the goaf is a steady state process, and eventually the balance between oxygen concentration diffusion and reaction will be reached. In the process of gas extraction, nitrogen can play the role of inerting goaf for the area with high concentration of nitrogen, but the inerted area is small. For the deep goaf, the injected nitrogen does not play the role of inerting, but only acts as a substitute for air leakage in the goaf, and the inerting effect is not obvious.