Abstract: In this paper, the spontaneous combustion marker gas and its critical value in the 8₂ coal seam of Qidong Coal Mine are studied.The 8₂ coal seam has a strong tendency to spontaneous combustion, and the geological conditions are complex, and the hydrogeological conditions have an impact on the monitoring of spontaneous combustion.Through the standardized temperature rise experiment, it was found that the concentrations of CO and C₂H₄ gases increased significantly with the increase of coal temperature, which could be used as key marker gases.CH₄,C₂H₆ and C₂H₄ are directly related to the increase of coal temperature, and the detection of C₂H₈ indicates that the coal temperature exceeds 110 ℃,which can be used as an early warning reference.No C₂H₂ was detected in the experiment, which is speculated to be related to the experimental conditions and the characteristics of the coal sample.The study provides a scientific basis for the risk assessment and preventive measures of spontaneous combustion in Qidong Coal Mine.