Abstract: The mechanism of the pyrite thermal decomposition toasted in conventional ways fitted to the unreacted core model.In this paper, the pure pyrite (-0.074 mm) was roasted respectively at the temperature of 600 ℃, 650 ℃ and 700 ℃ in the argon atmosphere in microwave oven.And the purpose of this paper is to make a research on the kinetics of thermal decomposition reaction of pyrite roasted by microwave.The test results were simulated by the unreacted core model and the homogeneous reaction model.The results indicate that the thermal decomposition of pyrite in microwave follows the homogeneous reaction model, and the mechanism function of this reaction is dx/t=k(1-x).Compared with conventional calcinations, microwave could reduce the activation energy of the reaction by 148.65 kJ/mol.