In order to investigate the effectiveness of treatment measures for silt subgrade in high seismic fortification areas, vibration table model tests were conducted on pure silt subgrade and reinforced silt subgrade. Based on a comparative analysis of the failure characteristics and dynamic response laws of the two models, the influence mechanism of reinforcement on the seismic performance of silt subgrade was explored. The experiment shows that after the peak acceleration of seismic load reaches 0.25 g, the experimental pure silt subgrade gradually experiences cracking, fragmentation, and sinking failure. After adding four layers of geogrids on the slope side of the subgrade, the seismic resistance of the silt subgrade can be effectively improved. When the peak acceleration of the seismic load is loaded to 0.35 g, although cracks also appear on the reinforced silt subgrade, the subgrade can still maintain good integrity. Under seismic loads, reinforced silt subgrade and pure silt subgrade have basically the same acceleration and dynamic soil pressure response rules. The acceleration amplification factor increases nonlinearly with the increase of subgrade height, and decreases with the increase of seismic load. Under the same load, the amplification factor on the slope side of the subgrade is larger than that on the centerline side, but the difference between reinforced silt subgrade is smaller. The dynamic soil pressure of both models shows a pattern of “larger on both sides and smaller in the middle” in the height direction of the subgrade. In the direction of the subgrade cross-section, the dynamic soil pressure on the centerline side of the subgrade is greater than that on the slope side. Due to the influence of subgrade structure, the potential fracture surface of reinforced silt subgrade under seismic loads will form at the end of the reinforced body and within the low pressure compaction zone. Reinforcement is an effective measure to improve the seismic performance of silt subgrades. In practical engineering applications, the length of the reinforcement should not be less than 0.65H, and there should also be sufficient anchoring length.