Abstract: The analysis of crack initiation and instability propagation of dam concrete needs to simulate the weak discontinuity between aggregate and mortar as accurately as possible. The micron thickness of the interface transition zone makes the finite element mesh have the problems of poor mesh generation quality and large number of meshes. Zero-thickness cohesive interface elements were preset between the solid elements of different material interface. By reassembling subdomain interface configurations after presetting zero-thickness interface elements, the aggregate-mortar-interface multi-scale domain decomposition finite element mesh was established. Meanwhile, the gradient-enhanced continuum damage model and the cohesion model were combined to simulate the failure of aggregate and mortar matrix, and the weak link between the aggregate and cement matrix in one model. A macro-meso concurrent multi-scale domain decomposition model for discontinuous deformation of dam concrete was constructed. The model was applied to the direct tensile test simulation of a dam concrete. Both of the random aggregate models could capture the whole process from weak connection to disconnection of the interface between aggregate and mortar. The failure modes reproduced of concrete specimen were in agreement with the results of reference papers, proving that the model is reasonable, and can provide technical support for the numerical study of damage and fracture mechanical properties of dam concrete.