Abstract: Through a series of direct shear tests under different vertical stresses, digital visual tracking technology and non- punctuation soil deformation measurement techniques are adopted to study the macroscopic and mesoscopic behaviors of the interface between biaxial geogrid and sand. The distribution laws of soil pressure near the reinforcement soil interface are analyzed, and the changes of interface movement and mesoscopic fabric evolution characteristics are studied. The results show that the distribution of the vertical pressures decreases from the front to the back end on the near direct shear reinforcement interface. The direct shear displacement is up to 25 mm, and a stable shear strain concentration zone is formed. In the range of reinforcement interface 6 to 8 times D₅₀ particle size thickness, the sand particle particles on the interface exhibit rotational and translational displacements, and outside this range, the particles show translational displacement along the shearing direction, and the displacement is smaller. During the shearing process, the interface particles rotate, soil dilatancy occurs, the porosity increases, the coordiation number decreases, the particles are re-compacted, the porosity decreases, the coordiation number increases, the particles along the long axis orientation tends to be horizontal direction, and various meso fabrics are in relatively stable state.