In order to uncover the effect of pyrite on the tendency of coal to spontaneously combust, thermal analysis was carried out to characterize the reaction process of coal with different pyrite contents at four heating rates of 5, 10, 15, and 20 K min(-1) in air flow from 25 to 900 degrees C. The Flynn-Wall-Ozawa method was applied to calculate the activation energy of coal with different pyrite contents. The results show that the thermogravimetric (TG) curve of coal samples can be divided in four stages, being water evaporation, oxygen absorption, thermal decomposition and burnout. As the mass fraction of pyrite content increased, the ignition point of the coal samples decreased and the weight loss rate during the thermal decomposition phase diminished. Meanwhile, the exothermic peak and mass loss peak moved toward lower temperatures. The peak values in the derivative thermogravimetric (DTG) and differential scanning calorimetry (DSC) curves shifted to higher temperatures with higher ignition and burnout temperatures under faster heating rates, but the whole curve shape was not affected. The apparent activation energies of the coal samples declined with higher pyrite contents, so the spontaneous combustion of coal can be promoted by pyrite. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.