A test device for the pullout test of reinforced bar in the rockfil has been designed. After that, a series of pullout tests for the ribbed steel bars in rockfill were carried out, and the shear characteristics of contact interface in the reinforced rockfill were studied. The experimental results show that the relationship curves between shear stress and shear displacement of the contact surface is obviously nonlinear, and the shape is similar to the parabola at the lower end. Meanwhile, the influence of overburden pressure on the test results is larger, and the peak and residual shear stress increases with the increase of overburden pressure, while the peak shear displacement decreases gradually. In addition, a damage constitutive model of contact surface is established based on the theory of damage mechanics, which can better simulate the influence of overlying pressure on the shear characteristics of contact surface and the nonlinear characteristics including the strain hardening, the strain softening and the residual state.