Abstract: This paper is based on a case history of a landslide occurred at the soil-rock interface. By mixing different ratios of medium sand, silicon powder and cement, rock specimens with different shapes of surface and compressive strengths are constructed to model the rocks of different degrees of roughness and weathering. The strength behavior of gravel-rock interface is investigated through laboratory large-scale simple shear tests. The results show that the shear strength of gravel-rock interface varies significantly with the shape of rock surface. The larger the surface undulation, the higher the shear strength, and the closer the shear strength is to that of the gravel. The shear strength of zigzagged interface with h=20 mm is greater than those with h=10 mm and h=0. The magnitudes of the shear strengths of gravel-rock interfaces with the same undulating height are as follows: waved interface>staged interface ≈ zigzagged interface>singly-bulged interface. The degrees of damage due to shearing are different for rocks with different degrees of weathering, which are modeled using rock specimens with different compressive strengths. The shear strength of interface changes with the degree of damage. The degree of weathering of rock is an important influencing factor on the shear strength of gravel-rock interface. A shape parameter and a damage parameter are used to characterize the effects of the shape of rock surface and the degree of weathering on the gravel-rock interface, respectively. By using these two parameters, an equation is proposed to estimate the shear strength of gravel-rock interface. It provides a theoretical basis for the stability analysis of soil-rock slope.