Abstract: Current numerical models for electromechanical impedance method often fail to accurately simulate concrete’s heterogeneous structure and micro-damage evolution. To overcome this limitation, a mesoscale simulation framework was developed to capture the influence mechanism of material heterogeneity and damage progression on admittance responses, with balanced fidelity and computational efficiency. Three-dimensional mesoscale modeling, an equivalent spectral element method, and a phantom node method were integrated to enable high-fidelity, efficient simulations from static material characterization to dynamic crack propagation. Results show that the 3D mesoscale model accurately reproduces the effect of aggregate volume fraction on admittance characteristics; the aggregate distribution and shape have negligible influence. The developed equivalent spectral element method preserves heterogeneity while reducing computational cost, supporting broadband, high-accuracy admittance simulation and damage sensitivity analysis. By introducing the virtual node method, crack propagation is simulated continuously on a fixed mesh, eliminating repeated remeshing and significantly improving the computational efficiency for simulating multi-step damage detection.