Abstract: The permeability of rock represents its ability to pass through fluids. In order to solve the problem of low permeability of reservoir rock and low amount of resource exploitation during the mining process of sandstone gas and shale gas, the authors had studied to simulate the actual high pressure state of the rock in deep underground by the high temperature and high pressure true triaxial test machine self-developed by Taiyuan University of Technology. The evolution laws of the permeability of sandstone at 100～400 °C under true triaxial stress state are explored. The results show that the permeability of sandstone decreases slowly from 100 to 280 °C, the permeability value is on the order of 10-16～10-17 m2 . After the permeability threshold temperature is 280 ℃, the permeability of sandstone increases several times up to 10 times with the maximum increase of 46 times, and the permeability tends to be stable at 340 ℃ on the order of 10-15 m2 . At the same time, the results verify that the stress state of the rock has a direct influence on the permeability. For the sandstone under the same confining pressure, the maximum principal stress of the specimen has a larger increase in the permeability in the direction of the maximum principal stress before and after the threshold temperature.