In order to study particle size Influencing loose coal of low temperature oxidation, a self-developed device is designed for low temperature oxidation of loose coal. The experiments were divided into three groups. The first group using a single particle size range of coal samples for low temperature oxidation experiments, the experiments show that the single particle size range of coal sample size is smaller, the greater the magnitude of the CO concentration, and the faster the accelerated phase of coal spontaneous combustion. Second groups were done with mixing multiple sets of two range of particle size of coal sample, which obtains the increase of particle size, the influence of porosity on the coal spontaneous combustion gradually transformed from the positive effect to negative effect, and the turning point of the particle size is about 3 mm. The third groups are of small size range and large size coal mixed coal mixed influence on coal spontaneous combustion, with the small range of particle size, the mixed coal particle size effects the spontaneous combustion of coal, not only affected by the size itself, but also by the size of the gap between the particle size and particle the size range. And with the increase of particle size, the effect of particle size and particle size range on coal spontaneous combustion is gradually weakened.