The temperature rise rate in oxidation process of gangue and coal specimen from Jingang Coal Mine has been investigated and the sulphur configuration in various kinds of gangue has been quantitatively analyzed to explore their spontaneous combustion mechanism. It is proved that the content of FeS 2 is very high in gangue of Jingang coal mine. A great deal of heat is released with the oxidation of FeS 2 in pyrites, the accumulation of heat results in gangue spontaneous combustion when the temperature reaches a certain degree.