Abstract: For the serious situation of coal spontaneous combustion hazard in Xuandong No. 2 Coal Mine Ⅲ₃ coal seam, we use Fourier transform infrared spectroscopy to study the microstructure and law of coal and oxidation in the process of active group change from the microscopic view. The results showed that Xuandong No. 2 Coal Mine Ⅲ₃ coal seam samples contained less overall number of active groups, compared with other high spontaneous combustion tendency of coal samples should have lower tendency. Low temperature oxidation of coal was mainly composed of a hydroxyl group, saturated and unsaturated hydrocarbon side groups caused. Main reasons of serious mine spontaneous combustion disasters were considered other factors, such as external moisture, temperature, geology, ventilation, etc.