Abstract: Soilbags have been used to prevent frost damage to canal expansive soils in cold regions. The mechanical characteristics of the interface between soil bags and canal expansive soil is a key factor for the design of the canal slope. The direct shear tests of soilbag-expansive soil interface with various water contents under positive and negative temperatures are conducted by a self-developed direct shear test device. Effects of temperature and water content on shear characteristics of the interface are studied. Test results show that: frozen samples exhibit typical strain softening failure, while the samples under positive temperatures show two failure patterns of weak strain softening and hardening. Under negative temperatures, as water content rises, peak shear strength and interfacial cohesion increase gradually, while the residual shear strength is almost unaffected. Under positive temperatures, peak and residual shear strength, interfacial cohesion and friction angle decrease with increasing water contents. Normal displacement of the frozen sample demonstrates a three-stage growth trend and exhibits shear dilatancy behavior. At positive temperatures, the sample shows shear dilatancy under low stress and shear contraction under high stress. Under identical normal stress, samples with optimal moisture content demonstrate the least final dilatancy displacement.