Abstract: In order to study the cooling law of liquid carbon dioxide on coal samples, the characteristic temperature of coal samples was obtained by temperature-programmed experiment. Liquid carbon dioxide cooling experiments were carried out for coal samples with different particle sizes to analyze the influence of coal sample particle size on liquid carbon dioxide cooling. The experimental time was divided into three stages with the characteristic temperature of coal as the node, and the relationships between the temperature drop of liquid carbon dioxide and the characteristic temperature of coal sample was constructed. The experimental results show that the cooling effect of liquid carbon dioxide is better with the larger particle size of coal sample.