Abstract: In order to study the coal oxidation characteristics of Yili Gangou Mining Area, the coal samples with different particle sizes in Yili Gangou Mining Area are analyzed by thermogravimetry(TG), different characteristic temperatures are obtained, and to calculate the activation energy of different stages(room temperature-T₂ stage, T₂-T₅ stage, T₅-T₆ stage, T₆-T₈ stage).With the help of FTIR, the characteristics of functional group changes in coal samples of different particle sizes are analyzed, the infrared spectra of different spectral bands are fitted by peak sub-peaks, and the peak area and peak area ratio changes of functional groups of coal samples with different particle sizes are calculated, and the infrared spectra of different stages are peak-fitted, and the peak area and ratio changes of the functional groups of coal samples of different particle sizes are calculated.The research results show that with the decrease of coal sample particle size, each characteristic temperature point basically changes little; with the decrease of particle size, the room temperature-T₂ stage activation energy shows a fluctuating trend, and T₅-T₆ stage increases first and then decreases, the activation energy of T₂-T₅ stage and T₆-T₈ stage show a decreasing trend and coal samples with a particle size of 80-96 μm have the smallest activation energy at room temperature-T₂ stage, T₂-T₆ stage, and T₆-T₈ stage, and the reaction is more intense; as the particle size of the coal sample decreases, the absorbance of all functional group increases, the hydroxyl group in the coal molecule is relatively stable, the methylene group in the aliphatic groups has higher reactivity, and the oxygen-containing functional group has the largest proportion of phenolic hydroxyl C—O stretching vibration.The disubstituted benzene ring of aromatic hydrocarbons gradually disappeared.