Abstract: In order to study the early prediction and forecast of the spontaneous combustion risk of upper stratified old coal area in steeply inclined and extra-thick coal seams, taking the fresh coal samples (initial oxidation) and oxidized coal samples (secondary oxidation) of weakly cohesive coal in Wudong Coal Mine as the research object. The characteristics of secondary oxidation of spontaneous combustion of weakly cohesive coal and the micro-variation characteristics of pre-oxidized coal samples were studied. In this experiment, the release law of gaseous products was studied by using a programmed temperature-rising device. The exothermic characteristics of initial and secondary oxidized coal samples were measured by DSC differential scanning calorimetry and the functional groups of coal samples were pre-oxidized by infrared spectroscopy at different temperatures. The results showed that the concentration of oxygen, the rate of generation and the exothermic intensity of secondary coal were lower than that of initial oxidation. With the increase of pre-oxidation temperature, the content of oxygen-containing functional groups gradually increased, the content of aromatic hydrocarbons decreased, aromatic ring content was basically unchanged.