The oxidation of pyrite under high temperature is the main reason led to the emission of SO2 during the cement production process.A onedimensional furnace was adopted to investigate the oxidation of the pyrite under high temperature and suspension state.XRD analysis and the test of LOI on the oxidation product were made.XRD analysis showed that no oxi dation reaction of the FeS2 occurred under 300 ℃，and the diffraction peak of Fe2O3 was observed from 400 ℃.With the incre ase of temperature，the diffraction peak intensity of FeS2 decreased，while the Fe2O3 increased significantly.Besides，the only oxidation product of FeS2 at 400~800 ℃ was Fe2O3.Based on the test results of LOI，less FeS2 went through the oxidation reac tion under 300 ℃ within the 10 s reaction time 10 s，which was accordance with the XRD analysis.The oxidation rate of FeS2 under 400，600 ℃ and 800 ℃ were 50%，85% and 92% respectively.These results were further applied in the actual cement production process，and it indicated that about 64% FeS2 was oxidized during the process of C1~C4 preheaters.