To verify the feasibility and effectiveness of using silt as subgrade fill in regions with high seismic fortification requirements, three model types were designed and fabricated: plain silt subgrade, reinforced silt subgrade, and 4% cement-improved silt subgrade. The failure characteristics and dynamic response patterns of the three schemes were investigated through shaking table tests, and measures to enhance the seismic performance of silt subgrade in high seismic fortification areas were explored. The results indicate that the plain silt subgrade progressively underwent cracking, crushing, and subsidence failure after the peak seismic acceleration reached 0.25g. Both the reinforced silt subgrade and the 4% cement-improved silt subgrade exhibited superior seismic resistance. When the loading on the reinforced silt subgrade reached 0.325g, and that on the 4% cement-improved silt subgrade reached 3.5g, cracks appeared in both models, yet they maintained good structural integrity. The acceleration amplification factor within the three subgrade models decreased with increasing seismic load, whereas the dynamic earth pressure increased nonlinearly with increasing load. When cracks and damage appeared in the subgrade, the acceleration amplification factor decreased markedly, and the dynamic earth pressure also decayed. Provided that construction quality is ensured, using plain silt for subgrade filling can satisfy seismic fortification requirements. Reinforcement and cement improvement are effective approaches for enhancing the seismic performance of silt subgrade and can be prioritized in regions with high seismic fortification demands.