As a widely used structural material, the micro-crack problem of concrete seriously affects the durability and safety. Inspired by the phenomenon of biological self-healing, microcapsule self-healing technology provides a new way for self-healing of cracks. In order to study the influence of microcapsule parameters on the mechanics and self-healing properties of cement-based materials, a mesoscopic fracture model of microcapsule-cement-based composites considering material heterogeneity was established based on the lattice model theory. By simulating the fracture process of the material under uniaxial tensile and compressive loads, the weakening effects of microcapsule content (from 1% to 3%) and particle size (from 176 μm to 245 μm) on its strength, elastic modulus, stress-strain relationship and crack propagation law were systematically analyzed. The numerical simulation results show that the incorporation of microcapsules will form a weak area, resulting in a significant decrease in the strength of the matrix, and the decrease will increase with the increase of the content and the particle size. At the same time, the model successfully simulated the repair process, and found that the microcapsules had a clear repair effect on the mechanical properties. The compressive strength repair rate under the optimal parameter combination (content 2%, particle size 205 μm) can reach 96%. This study provides an effective numerical analysis tool for the performance prediction and parameter optimization of microcapsule self-healing cement-based materials.