Abstract: The deformation and mechanical characteristics of rock fills in the construction of high earth-rock dams will be changed along with the temperature, which directly affect the deformation and safety of the dams. Through rheological tests on the rock fills under high, normal or low temperatures and different temperature cycle times by using the large degradation triaxial instrument, the effect of temperature on the strength and deformation of the rock fills is studied. The conclusion is drawn as follows: the deformation of rock fills is influenced by the temperature, the deformation decreases when the temperature increases, and the more the temperature cycle times, the higher the final axial deformation. Along with the increase of the temperature in rheological tests, the final axial deformation decreaseds, with the increase of the number of cooling or heating, and the final axial and volumetric deformations decrease. It is believed that the temperature cycle has a certain degree of damage to the rock fills, resulting in the decrease of the particle strength and the increase of the deformation, and the deformation is not obvious until the degradation of rock fills is completed after many times of the temperature cycle.