Abstract：According to the characteristics of high slope rock mass of the permanent ship-lock in the Three Gorges Project，some typical rock mass is chosen for physical simulation. The size of unloaded specimen is 0.25 m×0.25 m×0.25 m，and the corresponding actual sizes are 0.75 m×0.75 m×0.75 m，2.25 m×2.25 m×2.25 m，6.75 m×6.75 m×6.75 m，and 20.25 m×20.25 m×20.25 m. The problems of size effect of unloaded rock mass，i.e. stress-strain relation，the compressive strength，the deformation modulus (compressive and tensile)，the Poisson’s ratio，and the anisotropic characteristics，are studied. Some significant conclusions are put forward，and the mechanical parameters are suggested to consider size effect.
