Abstract: By use of the image visual tracing technique and non-target measuring technique, laboratory mesoscopic model tests are carried out to study the rules of particle rotation and shear strain concentration zone from a mesoscopic view. On such a basis, the model of particle flow code in 2-dimension (PFC2D) is established by developing elliptical clump particle to simulate the true sand samples and by using parallel-bond model to simulate the geogrids. The shear strain concentration zone, the sand particle movement trajectory and the rotation characteristic of the interface between soil and geosynthetics are studied. The rules of the reinforced soil interface with some mesoscopic-parameters such as coordiation number, local porosity and sliding fraction are further studied. The study results can provide a new understanding for future studies on the mechanism of the reinforcement interface.