Abstract: In order to research the characteristics of the thermal oxidation reaction of coal by using thermogravimetric technique, the thermal mass loss and oxidation of bituminous coal with different moisture and different particle size were investigated under a heating rate of 10 ℃/min. Low-temperature pyrolysis kinetics model is developed by using Coats-Redfern integral method. Results show that the two-step oxidation process of bituminous coal was mainly affected by water evaporation and gas desorption, mass-gaining and structural oxidation. With the increase of moisture, the temperature thresholds lying in the first step fist decrease and then increase, and the temperature thresholds of sample S3 with moisture of 9.16 % are minimum, therefore, moisture has a significant effect on the first stage reaction process; however, the temperature thresholds lying in the first step and the spontaneous combustion threshold increase with the increasing particle size. A first-order and second-order reaction models are proposed respectively for describing the two-step reaction process with the correlation coefficient R² greater than 0.98, thus, kinetic compensation relationship exists between oxidation activation energy and frequency factor. Compared with the other coal samples in the same group, lower apparent activation energy was required by the sample S3 with 9.16 % moisture content and the sample L5 with the smallest particle size(19.21 μm) to overcome the reaction barrier, which indicated that it has a high risk of spontaneous combustion.