Abstract: The deformation and shear strength parameters of soil-rock mixtures are mainly affected by the stone content, stone shape, nature of soil and water. Nowadays, the study mainly focuses on the three former aspects. The effect of water on the mechanical properties is rarely studied. This paper uses the pebbles, silty clay and water to make soil-rock mixture samples and carrys out large-scale direct shear tests. The test results show that as the shear displacement of model increases, the shear stress-displacement curve of soil-rock mixtures can be divided into three stages: linear deformation stage, initial yielding stage and hardening stage. The interaction of ratio of water and ratio of pebbles affects the mechanical properties of soil-rock mixtures. Overall, the shear strength of mixtures decreases as water content increases. The trend of decrease is slow at first, and then becomes rapid, and slow down again. For the same rock content, the internal frictional angle experiences two stages of decline process as the water content increases. Firstly, it decreases slowly when the water content is low. Then it decrease rapidly when the water content is high.