The spontaneous combustion mechanism of sulfide minerals powder is studied by simultaneous thermal analysis. The chemical reactions of pyrites in the atmospheres of air and nitrogen are deduced and the corresponding reaction products are characterized by the Raman spectroscopy. The characteristic temperatures of the pyrite reaction process are discussed in different conditions. The results show that the process of oxidation spontaneous combustion can be divided into three stages. Fe3FeSiO4(OH)(5) in the minerals is decomposed at low temperature in the oxidation process. FeS2, the main component of the mineral, is mainly oxidized in the stage of oxidation spontaneous combustion. However, FeS2 will be decomposed under heating in nitrogen atmosphere. Thermal stability of pyrite in air is lower than that in nitrogen, and its thermal stability will be improved by increasing heating rate and particle size. (C) 2016 Elsevier B.V. All rights reserved.