Abstract: In order to solve the problem of “three zones” division of spontaneous combustion in goaf of fully mechanized coal face and design and optimization of nitrogen injection parameters under the condition of hard roof of crushing soft outburst coal seam, three zones of spontaneous combustion on the inlet and return sides are measured by buried pipes in the inlet and return air lanes. The distribution of the three zones in the middle of goaf is determined by numerical simulation and image processing, and nitrogen injection parameters are given. The research shows that under the condition of hard roof of crushing soft coal seam, the width of the dispersion zone and the oxidation zone in the goaf is obviously widened, and the optimal N2 injection outlet is at the junction of the dispersion zone and the oxidation zone. However, it is difficult to inject N2 into the towed tube because of the deep burial. Therefore, by increasing the N2 injection amount and reducing the N2 injection depth, the optimal N2 injection amount is 600 m3/h to 800 m3/h when the N2 injection pipe is injected at the buried depth of 30 m. There is a corresponding relationship between the CO distribution and the “three zones” in the goaf. The minimum safe advancing speed of the 24311 working face is 1.89 m/d. The safety ventilation of working face is 119 m3/min.