Abstract: In order to explore the influence of thermal effect on pore structures and adsorption properties of coal, mercury penetration experiments with the coal samples under the water bath temperatures of 40 ℃, 60 ℃ and 80 ℃ and isothermal adsorption experiments of 30 ℃ with coal samples were carried out. The results show that the total pore volume, pore specific surface and porosity of the coal sample increased with increasing temperature of water bath. Every pore has different changing trends of pore volume ratio, and the growth rate of coal porosity increases with temperature from 60 to 80 ℃ is far greater than the temperature from 40 to 60 ℃. The higher of the water bath temperatures of coal samples are, the higher pressures of the gas balance pressure require to reach the absorption maximum. The adsorption constant increases with the temperature of the water bath, but the value of water bath temperature from 60 to 80 ℃ increases less than the temperature from 40 to 60 ℃.