In order to study the dynamic response characteristics of sluice gates on soft foundation in Dongting Lake area under earthquake load, Sujiaji Drainage Sluice Gate in the tailrace of Yuan Shui was selected as a typical case, and FLAC3D finite difference software was used to simulate the three-dimensional numerical power of Sujiaji Drainage Sluice Gate under the action of water pressure, and to comparatively evaluate the change rule of vertical settlement under static and dynamic loads. In the process of numerical calculation, the horizontal down-river-oriented seismic wave that had been filtered and baseline correction processed was input to the bottom of the model to monitor the acceleration response under the gate chamber, vertical settlement deformation, super pore water pressure, and increased in effective stress over the course of time. The results show that the settlement rate of the soil body would be accelerated under the water pressure, while the localized uplift of the critical surface under the guide wall also could be suppressed. Seismic waves traveled with a time delay from the bottom to the top, and the rate of increase of the acceleration response value was easily affected by the strength of the soil layer. During the seismic action, the fill on the soft soil layer will continuously squeezed other areas, resulting in a positive relationship between the pore water pressure and effective stress and the seismic acceleration amplitude. This study provides a reference for the design and safety of similar projects.