Abstract: The composite liner consisting of needle-punched GCL and textured geomembrane (GM) is widely used, and changing temperature environment can be encountered when it is used to deal with mining-smelting waste or municipal solid waste. Aiming at the temperature effect of the shear strength of the composite liner, the large-scale temperature-controlled water-bath direct shear apparatus is used to carry out the whole shear tests without pre-determined failure surface for the hydrated needle-punched GCL+GM composite liner at different temperatures. The shear strengths of the composite liner in the range of 10℃~70℃ are obtained, and the shear characteristics of the composite liner under different temperatures as well as normal stress are revealed. The test results show that obvious peak strengths and obvious post-peak softening phenomena occur at the stress–displacement curve at all the test temperatures. The peak shear strength and large-displacement shear resistance of the composite liner achieve the maximum value at the room temperature of about 20℃, and either increasing or decreasing temperature can cause obvious reduction in the shear strength of the composite liner. The change of temperature has a significant effect on the shear strength and failure modes of the composite liner, and accordingly attention should be paid to the temperature effect on the stability of slopes containing geosynthetics.