Recent researches have proved that the shape of particles has significant effect on the mechanical behavior of granular materials. Therefore to model the appropriate behavior of granular assemblies, it's very ideal that they become simulated as accurate as possible. The method that is applied in this paper simulates grain shapes close to reality. In this way, shape of a particle is modeled by combining a set of overlapping spheres, which are connected to each other in a rigid way. A program that is based on Discrete Element Method (DEM) has been developed to generate different real grain shapes. In order to investigate the influence of grain shape on mechanical behavior of granular soil, four groups of grains with different angularities, including high angular, medium angular, round, and spherical, are generated. Several triaxial tests with different confining pressures and friction coefficients have been carried out on assemblies with different grain shapes. The results prove that angularity of grains considerably affects the behavior of granular material. (C) 2012 Elsevier B.V. All rights reserved.