To investigate the influence of soil particle size on geogrid-coarse soil interface cyclic and post-cyclic shear strength behavior, a series of large scale direct shear tests, cyclic shear tests and post-cyclic direct shear tests is conducted through a large-scale direct shear device. The influence of cyclic shear history on interface shear behavior is studied according to the comparison and analysis of the results obtained from direct shear tests and post-cyclic direct shear tests. The results show that, in direct shear tests, the interface apparent cohesion and friction angle both increase with soil particle size increase. In cyclic shear tests, the shear strength tends to harden under different particle sizes; for the same amplitude of cyclic shear displacement, the smaller the particle size is, the faster the hardening rate of interface is. After subjected to cyclic shear, the ratio between residual shear stress and peak shear stress of interface decreases; and the peak apparent shear stress increases insignificantly.