To study the cumulative plastic deformation characteristics of saturated silty soil under subway loads, the GDS cyclic triaxial testing system was used to test the saturated silty soil near the Guoquan Road, Shanghai Metro Line 10. The effects of vibration frequency and dynamic stress amplitude on the cumulative plastic strain were considered. The experimental results show that the cumulative plastic strain increases with the dynamic stress amplitude, and with the same dynamic stress amplitude, the cumulative plastic strain increases as the frequency decreases. By an analysis with the 2² factorial design method, it was found that the vibration frequency, the dynamic stress amplitude, and the interaction between the two have a significant effect on the cumulative plastic strain. Based on the theory of regression analysis, the nonlinear equation of cumulative plastic strain was established, which considers the vibration frequency, the dynamic stress amplitude, and the interaction between the two, and the equation was tested. The research results can provide a valuable theoretical basis for controlling the subsidence induced by subway operation.