Abstract: The accumulation bodies composed of soil-rock mixture are widely distributed in China. The deformation and stability of huge and large-scale loose accumulation bodies in reservoir areas are extremely concerned during construction of hydroelectric projects. Aiming at the complex property and material composition of accumulation slopes, the typical accumulation slopes in Three Gorges Reservoir region are studied through field investigation, sampling and laboratory tests. The influences of stone contents on the relationship between shear stress and displacement and soil strength parameters are analyzed by using the large-scale direct shear tests. Mechanical properties and deformation of accumulation bodies are controlled by the stone contents. With change of the stone content, the relation curves of shear stress and displacement are classified into three types: exponential curve, hyperbolic form and strain softening. The cohesion of accumulation body increases with the increment of the stone content in the form of quadratic polynomial curve, and generally it reaches the peak value when the stone content is about 60%, then it decreases as the stone content increases. The internal friction angle increases with the increment of the stone content in the form of exponential curve.