During the process of drilling and gas injection in coal seam，under the external force disturbance，the axial or circumferential load on coal seam will change significantly. The pore and fracture in coal seam will change dynamically due to stress change and then the permeability of coal seam also changes dynamically with variation of gas types. Using the No.9 coal seam in Ningwu basin as the research object，the self-developed triaxial gas seepage experiment device was used to study the permeability variation of coal samples with increased confining pressure，and also the relationship between permeability-strain and stress-strain while axial press was increased to damage coal samples by using He，CH4，CO2 respectively. The results show that in the process of increasing confining pressure，at the initial stage the permeability of coal sample for He is the largest，moderate for CH4，smallest for CO2. With the increase of confining pressure，the effective stress increases and the permeability decreases. While stress is being increased to broken the coal seam at the direction of axial press，the permeability-strain curves and stress-strain curves are basically identical，but the change of permeability lags behind the change of stress and the greater the gas adsorption，the more obvious the lag effect.