Abstract: The hydraulic tests were conducted on geosynthetic clay liners (GCL) containing granular Na-bentonite under different temperatures and pressures, using the GDS geoenvironmental permeameter. Under low pressures, the hydraulic conductivity decreases with the temperature, and will be gentle or slightly increases when the temperature is over 50-60 ℃. Nevertheless, the hydraulic conductivity decreases with the temperature under the pressure of 100 kPa. The intrinsic permeability decreases with the temperature, which is more significantly under low pressures. Therefore, a great difference exists between the estimated and the measured hydraulic conductivities when only considering the change in physical properties of the fluid with temperature. The adsorbed water content of bentonite decreases with the temperature, resulting in the estimated hydraulic conductivity less than the measured value and intrinsic permeability increasing with temperature, which cannot explain the permeability of GCL. With the increasing temperature, the granular bentonite will transform into the montmorillonite gel. Under low pressure, the distance between montmorillonite in intraparticle pore decreases with temperature, resulting in the decrease in hydraulic conductivity and intrinsic permeability.