Abstract: Based on independent research and development experiment device, gas desorption contrast experiments about external water intrusion and without external water intrusion under the condition of different anxial pressure and confining pressure were carried out by coal samples from No.5 seam in Qianjiaying Mine. Under the same test condition, the gas desorption amount and gas desorption velosity in the course of external water intrusion exceeds the value of natural desorption, which indicates that the external water intrusion promotes the gas desorption. When the axial pressure and confining pressure is at 4 MPa to 8 MPa, the desorption amount and desorption velocity decrease with the increasing of anxial pressure and confining pressure, and the desorption amount and desorption velosity increase gradully after 8 MPa.