Abstract: In order to study the constant temperature oxidation characteristics of coal under the oxygen concentration of 5% and 21%, the coal sample of 3^# coal seam in Xinglongzhuang Coal Mine of Shandong Province was taken as the research object, and the experiment was carried out by synchronous thermal analyzer to obtain the thermal analysis curves (TG, DTG, DSC) at different temperatures, and grasp the change of mass and heat release of coal sample in the temperature rising and constant temperature oxidation stage, simultaneously, using the Coats-Redfern dynamic equation and lnln analysis method to caculate the activation energy during the oxygen absorption and weight increase stage and the constant temperature stage. The results show that in the continuous heating stage, when the temperature is below 103.1 ℃, both the oxygen concentration of 5% and 21% have little effect on the mass change, and comparing with the oxygen concentration of 5%, the heat absorption when the oxygen concentration is 21% is reduced. When the temperature is higher than 103.1 °C, the effect of 21% oxygen concentration on the mass change, heat release and activation energy of the coal sample is greater than the oxygen concentration of 5%. In the constant temperature stage, with the increase of the constant temperature, the mass change rate, oxidation heat release and activation energy of the coal sample showed an increasing trend, and the parameter under the oxygen concentration of 21% was greater than the oxygen concentration of 5%; in the same temperature, the quality change of coal sample under the oxygen concentration of 21% is more obvious than the oxygen concentration of 5%.