Abstract: Soil-rock mixture is a kind of special geological material and has a wide spread in nature. It is comprised of rock blocks, fine soil particleand pore which is filled in. With the increase and development of all kinds of large scale engineering construction, geological disasters related to soil-rock mixture has seriously affected and restricted the engineering construction and human safety. Thus, it is important to study the soil-rock mixture. In this paper, the contact characteristic of rock and soil in soil-rock mixture has been focused on from the perspective of meso-structure. In order to simulate the gravel-soil interface in soil-rock mixture, the interface element in FLAC3D was used and then a three-dimensional numerical model of soil-rock mixture containing interface element was built. The reasonable variation range of interface parameters was selected. By analyzing the numerical simulation results, the sensitivity of parameters was investigated. It was found that stiffness, especially the normal stiffness has the significant effect on stress-strain curve of the soil-rock mixture as well as the relative movement between gravel and soil. Cohesion follows and the influence of friction angle is minimal. By comparing with the model without interface element, the feasibility and rationality of three-dimensional model of soil-rock mixture containing interface element are verified. The application of interface element makes it possible to accurately describe the macroscopic deformation characteristics of soil-rock mixture and the interaction mechanism between the gravel and soil.