Abstract: The hard coal and soft coal from No.10 Mine in Henan Pingdingshan, Gaocheng Mine and Guizhou Xintian Mine was selected to carry out mercury intrusion experiments and gas desorption experiments under the condition of changeable pressure. The pore structure characteristics and gas desorption laws are analyzed. The results show that the desorption rate of all coal samples decreases from the maximum initial value with the time during the process of changeable pressure desorption. The desorbed gas amount is up and down under different pressure, the overall trend is gradually decreasing. While the pressure is below 3 MPa, the fluctuation increases sharply because the desorbed gas pressure in the connected mesopores and macropores is not sufficient to continuously overcome the capillary pressure. The soft coal has more desorption capacity than hard coal under the same pressure drop condition. The desorption rate of soft coal is faster and the accumulated desorption amount is more.