Abstract: The coal-water interaction is of great significance for gas extraction and disaster prevention. Combined with 16 water vapor sorption models and the analysis of physicochemical structure of coal samples, the water adsorption behavior of low-rank and high-rank coals was studied. Results show that: the modified GAB model can better characterize the behavior of coal adsorption water, and the single-layer saturated adsorption capacity of low-rank coal samples is higher than that of high-rank coal samples, while there are no obvious differences in multi-layer adsorption capacity for the two samples; based on the Dent and Freundlich models, it’s found that with the increasing in water content or relative humidity, the water adsorption mechanism transforms from monolayer, multilayer to condensation successively; the differences in water adsorption behavior between low-rank coal and high rank coal are closely related to the number of oxygen-containing functional groups and the development degree of pore structure.