Abstract: In order to research the influence of the size distribution of residual coal for the heating and oxidation, the residual coal was divided into five groups in goaf, and the proportion of each group accounted for the overall was calculated respectively. Then heating and oxidation test for the five groups and composite particle coal samples were respectively carried out. The test results showed that the particle size distribution density of residual coal in goaf firstly increased and then declined with the increase of particle diameter. Oxygen consumption rate of different size coal samples changed exponentially with temperature increasing. Oxygen consumption rate of coal sample with composite particle size was consistent with the weighted average rate of coal samples with different particle size at the same temperature.