The contact surface of soil-rock have special engineering geological properties, in order to investigate the shear characteristics of soil-rock interface, a series of specimens with different contact surfaces were preparation, and direct shear tests were carried out. The particles distribution and constitutive model of shear plane were analyzed. Research indicates that: (1) The stress-strain curve of contact surface shows the characteristics of elastic-plastic variation. The logarithmic friction constitutive model of contact surface can better reflect the stress-strain relationship of contact surface in shear progress. (2) Particles on shear plane breaks and moves in the shear progress. The force required to breaking is greater than moving, which presented as different of shear strength macroscopically. In addition, the normal deformation is caused by the close and particle redistributable of contact surfaces. (3) In the lower normal stress, the contact surface is weaker than components. As the normal stress increases, the shear strength of contact surface increases and is located between the components.