Abstract: Compared with the widely used sand and gravel, the cemented sand and gravel (CSG) has certain cementing force and structure, and its macroscopic mechanical properties show obvious characteristics such as strain softening, dilatancy and cracking damage. Therefore, the traditional soil strength criterion and constitutive model are difficult to accurately describe its mechanical deformation mechanism. In this study, a binary strength criterion based on the binary medium theory is proposed. The criterion is a concave curve that decreases first and then increases on the meridian plane, and a smooth convex curve between the Drucker-Prager criterion and the unified nonlinear strength criterion on the π plane. The strength characteristics of CSG under different gel content content are described by one expression. Based on the strength criterion and mechanical characteristics of CSG, a double yield surface constitutive model is established, and the tangential modulus and tangential volume ratio are calculated by the hump curve. The triaxial shear test is simulated, and the simulation results are compared with the experimental data. The results show that the proposed constitutive model has good applicability. The model is easy to obtain parameters and implement numerically, and can be used to calculate the stress and deformation of CSG dam.