Abstract: Current research on microbially induced soil stabilization primarily focuses on the physical and mechanical properties of soils stabilized by Sporosarcina pasteurii, whereas investigations into the microstructural mechanisms remain insufficient. Consequently, this study adopts Staphylococcus to stabilize silty soils, with a specific focus on analyzing its microstructural characteristics. Through a comparative analysis of two calcium sources (calcium chloride and calcium acetate) and cementation solution concentrations ranging from 0.25 M to 1.0 M, a micro-scale investigation was conducted using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The results indicate that: (1) The interaction between calcium carbonate crystals and silt particles involves three patterns: pore filling, surface coverage, and inter-particle cementation; (2) Calcium sources and concentrations significantly influence the amount of calcium carbonate precipitation. Specifically, calcium chloride yields the highest precipitation at a concentration of 0.75 M, while calcium acetate outperforms calcium chloride at a low concentration of 0.25 M; (3) The calcium carbonate precipitates induced under all experimental conditions are identified as stable calcite crystals. These findings provide a theoretical basis for optimizing Microbially Induced Carbonate Precipitation (MICP) technology for silty soils and confirm the engineering applicability of biomineralization technology in the reinforcement of fine-grained soils.