In order to determine the influence of aggregate irregularity on the mechanical properties and failure morphology of concrete, Python programs were developed to generate randomly distributed aggregate models with different sharpness in ABAQUS, and the 0-thickness cohesive element and variable-thickness solid interface transition zone（ITZ）were established respectively. First, the reliability of model was determined by changing mesh size and friction coefficient between the loading pad and concrete compared with the experiment. Then, the quality of two ITZ modeling methods was analyzed. Finally, the uniaxial compression mechanical behavior of the three-dimensional meso-concrete model was analyzed from the aspects of stress-strain curve, fracture propagation, and energy dissipation. The simulation results show that the 0 thickness cohesive ITZ and the solid thickness ITZ model can predict the compressive strength of concrete, and the stress-strain curve and failure morphology of the ITZ model with solid thickness are more consistent with the experiment. The fracture propagation of concrete is obviously affected by the shape parameters of aggregate. The interior and surface of the spherical aggregate model are penetrating cracks. The strain energy of polyhedral aggregate model is larger, and there are many micro-cracks in the concrete, the possibility being compressed and destroyed into more fragments is higher. With the increase of aggregate irregularity, the compressive strength of concrete increases slightly, but the peak strain is not affected.