The coal permeability is very complex with significant stress sensitivity. A self-developed constant temperature ultra-low permeability measurement system combined with pulse decay method was used to carry out the gas permeability test on the tight coal in Longfeng coal mine, Guizhou province. The evolution law and influencing factors of permeability were studied systematically. Results show that: under constant hydrostatic pressure, the coal permeability is affected by effective stress and pore pressure, which tends to decrease first and then increase, there is a significant coupling effect between effective stress and pore pressures;the coal permeability decreases with the increase of effective stress or pore pressure in the form of a power function, and the decline rate gradually decreases, showing higher stress sensitivity, but the mechanism of effective stress and pore pressure is different;in the process of coalbed methane(CBM) extraction, the reservoir permeability can be increased by reducing the effective stress of reservoir to improve the drainage efficiency of CBM.