Abstract: In order to solve coal spontaneous combustion problem of 7₂ seam in Yuandian Mine effectively, the mark gas of spontaneous combustion was studied by temperature programming experiments on coal samples. By analyzing the gas generation laws at different temperature stages in coal oxidation process, the corresponding relationship between mark gas of coal spontaneous combustion and temperature is researched. The results show that the critical temperature of coal self-heating is 60 ℃ to 70 ℃ and the critical temperature of oxidation active stage is 120 ℃ to 130 ℃. Hence, CO was selected as the mark gas at 60 ℃ to 100 ℃ and the second fire index R2 was selected as the mark gas at 100 ℃ to 130 ℃. When the temperature was over 130 ℃, C₂H₄ was selected to be the mark gas and C₂H₆, alkane ratio φ(C₃H₈)/φ(C₂H₆) aand alkene-alkyl ratio are used as the auxiliary mark gas to determine the degree of spontaneous combustion of coal seam.