Abstract: Based on a meso-mechanical model of random aggregate, the mesh grid was partitioned by a characteristic unit scale of the material, and a three-dimensional meso-unit equivalent model was established for the researches on the damage process and macro-mechanical properties of heterogeneous concrete. The nonlinear finite element was used to numerically simulate the propagation process of cracks & fracture configuration and macro-mechanical properties in wet-screened concrete specimen under uniaxial tension /compression and in concrete trisection beams under bending load. The simulation results were compared with the two-dimensional results. It was found that: 1) compared with the plane model, a 3-D model could simulate the damage process of concrete under external loads more realistic, and could describe the macro-properties of heterogeneous concrete more accurate, and the computational results were in a good agreement with the experimental data; 2) the spatial distribution form of aggregate had a great influence on the damage process and damage path, but little impact on the macro elastic modulus and strength of concrete; 3) the method used in the paper had high efficiency, compared with other meso-mechanical models, such as a random aggregate model.