Abstract: As an effective seismic strengthening measure for the earth rock dam, the reinforcement is used more and more widely in the construction of high earth rockfill dams. A premise of the reinforcement design is the research on the contact characteristics and influence factors of the steel bar and rockfill materials. The authors of this paper, through laboratory pull-out tests, made studies of rebars and interface friction characteristic of the rockfill materials, and revealed the impacts of different overburden pressures, water content of rockfill, aggregate gradation and porosity factors on the test results. The experimental results show that the rockfill materials and steel contact shearing force and pull-out displacement curves show a parabolic shape with an opening at the lower end, which is steeper than that in the descending section, and the values of the residual shear stress are unstable. For the four influence factors, the overburden pressure and peak shear curves have approximately linear relationships; the porosity and the peak values of the shear curve are similar to a linear inverse relationship; the peak shear stress and the pull-out displacement curves of the trim level average are over the test curves of the grading of the upper envelope line. The peak shear stress and the pull-out displacement curves of the rockfill materials under the conditions of saturated water content are much lower than those under the dry conditions.