Low temperature oxidation of two different low rank coals was measured by in-situ FTIR. Curve-fitting analysis was employed to identify functional groups types of raw coals, and series technology was carried out on in-situ infrared spectrum of sample coals at low-temperature oxidation process to analyze the changes of main active functional groups with temperature. The results indicate that -CH3, -CH2, -OH, C=O, COOH are the main active functional groups in low rank coal. In the oxidation process, with temperature increasing, the methyl and methylene show the tendency of increase after decrease and then decrease, and all of hydroxyl, carboxyl and carbonyl group present the tendency of increase after decrease, there exists some differences among the main functional groups in the coal low-temperature process.
