Abstract: In order to study the laws of coal spontaneous combustion in the process of low temperature oxidation of coal samples near goaf, based on the industrial analysis of raw coal and water immersed and dehydrated coal samples, the microstructure and functional groups of raw coal and water immersed and dehydrated coal samples were analyzed by scanning electron microscope and infrared spectrum. The results show that:at the room temperature of 25 ℃, put the water immersed and dehydrated coal samples in water for a long time, rupture occurs in water absorption swelling of coal, the pore structure changes from compact to loose, the porosity increases, the contact area with oxygen increases, and the ability to absorb oxygen increases; groups containing oxygen near 1 800 cm^-1 （Ｃ＝Ｏ） peak becomes strong, accelerating the process of low temperature oxidation, some inorganic material decreases with the process of water loss away slightly, but the porosity increases; with the increase of temperature, functional groups containing oxygen of two coal samples increase, the process of low temperature oxidation is accelerated, the oxidation rate of water immersed and dehydrated coal samples is fast than raw coal.