Abstract: In order to study the variation of shear stress at the interface between reinforced soil and geogrid under normal cyclic loading, a large-scale dynamic direct shear apparatus is used to conduct the shear tests on the interface between gravel and geogrid with relative density of 75%. The effects of four initial normal stresses (20, 40, 60 and 80 kPa) and four normal load vibration amplitudes (10, 20, 30 and 40 kPa) on the interfacial cyclic shear characteristics are studied. On the basis of the tests, the expression for the normal stress at the interface before peak and at the residual stage under normal cyclic loading is established. Considering the influences of the initial normal stress and load vibration amplitudes, the expression for the interfacial shear stress-shear displacement is proposed based on the relative phase shift law. The results by the two proposed prediction expressions are in good agreement with the experimental ones, which verifies the correctness of the proposed method.