Abstract: In order to study the effect of soaking on coal spontaneous combustion,the coal samples with different ranks were selected,and the FT-IR and thermos-gravimetric experiments were carried out on the same moisture content of raw coal and soaked coal. Compared the Infrared Spectra,it is found that the active groups in the soaked coal increase and the oxidation activity is higher than that of raw coal. Based on the TG curves and the theory of ignition activation energy of coal spontaneous combustion,the activation energy of raw coal and soaked coal in the process of oxidization and spontaneous combustion was also studied. The results show that the water loss activation energy of soaked coal in- creases to 1. 01-1. 29 times of that of raw coal,which indicates that water is harder to evaporate in soaked coal under the condition of heating. The ignition activation energy of soaked coal reduces to 0. 51-0. 89 of raw coal,which indi- cates that the soaked coal is more prone to spontaneous combustion. The combustion activation energy of coal before and after soaking is basically the same,which indicates that soaking process does not affect the burning stage of coal. The thermal effect of raw coal and soaked coal in the process of oxidizing and spontaneous combustion was analyzed based on the DSC curves. It is found that the amount of heat released from soaked coal is increased to 1. 04 -1. 59 times of raw coal,which indicates that the soaked coal is more spontaneous from the point of heat.