Owing to rapid city development on gravelly formations, it is essential to evaluate the mechanical behavior of gravelly soil and predict its deformational response during construction. This study adopted the discrete element method to simulate the large-scale triaxial test of gravelly soil to elucidate the deformational behaviors, including nonlinear elastic and significant plastic deformation of gravelly soil. The results revealed that the simulated failure envelopes and stress-strain curves agreed with the test results. Considering the influence of the micro properties on the elastoplastic deformation characteristics, a higher plasticity index of the matrix decreases the elastic shear modulus. The particle shear stiffness and aspect ratio were the main factors that affected the variations in the plastic flow angle. The porosity and particle effective modulus significantly affected the plastic trajectory as observed in the plastic strain trajectory analysis. It was found that the denser the specimen and the larger the particle effective modulus, the smaller the plastic strain trajectory.