Soil resistance to a pile under lateral loading is usually estimated based on empirical p-y curves from field observations or simple laboratory tests. Due to the complex modes of deformation occurred in the soil around the rigid embedment, only simplified analytical solutions are available for granular soil. In this study, the three-dimensional discrete element code PFC3D is employed as a microscopic approach to investigate the soil resistance to rigid embedment. Various soil assemblages of different particle size distribution are generated and the soil resistance to a short rigid pile loaded laterally at depth is investigated in a numerical experimental program. The results from PFC are comparable to those from the common models in practice for lateral soil resistance to rigid pile. The soil resistance is influenced by the properties of the soil assemblage such as lateral earth pressure coefficient and particle grading. Particle grading also affects the displacement filed and the stress influence region during pile loading. In addition, the displacement pattern of the granular soil is also found to be different from that proposed for analytical solution for cohesive soil and the influence of the boundary condition on the p-y response of the DEM simulation requires further study.