FE analysis of plane strain compression tests on an unreinforced specimen and geogrid-reinforced sand specimens were conducted by nonlinear elasto-plastic FEM. The sand specimens was reinforced with 6 or 11 layers of geogrid. In the FE analysis. strength anisotropy, pressure dependency of strength, strain-hardening and -softening and shear banding (or strain localization) were considered for sand. The geogrid was modeled as a planar reinforcement in the plane strain FE analysis. By integrating the results from the FE analyses and the physical tests, the effects of reinforcement rigidity. covering ratio and interface friction angle on reinforcing effects and the dilatancy characteristics of reinforced sand were evaluated. A quantitative relationship was obtained between the reinforcement covering ratio of actual three-dimensional reinforcement and the equivalent interface friction angle in the 2-D plane strain FE analysis. Lastly, the effects and mechanism of the reinforced sand were evaluated based on the local stress paths within the reinforced sand.