Abstract: In order to explore the effect of particle size of different coal seams on the apparent activation energy of coal spontaneous combustion, combined with the coal spontaneous combustion program temperature system, the programmed temperature rise test was carried out on coal samples of different sizes in three coal seams of Qinglong Coal Mine. At the same time, the oxygen consumption rate, CO and C2H4 generation law of each group of coal samples are analyzed, and the critical temperature point and dry cracking temperature point of different coal samples can be obtained. According to the result, the low temperature oxidation process of coal is divided into three stages. The apparent activation energy and pre-exponential factors of different stages of each coal sample can be obtained by processing the experimental data by the established oxygen-dependent rate Arrhenius formula. The results show that for the coal samples in the same stage of change, the apparent activation energy will increase with the increase of the particle size. For coal samples of the same particle size, if the pre-exponential factor of the S1 phase changes little, the apparent activation energy will gradually increase as the reaction progresses；If the pre-exponential factor of the S1 phase changes greatly, the apparent activation energy of the S1 phase are greater than the energy of the S2 phase. The 5~7mm particle size is used as the critical particle size, and the apparent activation energy of the S1 and S2 phases are relatively larger than the apparent activation energy of other particle sizes. Coal samples with mixed particle sizes have small apparent activation energy at each stage. By comparing and analyzing the apparent activation energy of coal samples from three coal seams, it can be seen that, under the same condition the difficulty of spontaneous combustion in 17# coal seam is relatively large, followed by 16# coal seam and 18# coal seam.