Based on a triple-tower suspension bridge, using the finite element analysis method, the influence of elastic cable on the seismic response of the suspension bridge was studied, the seismic response of the bridge with the flexible central buckle was analyzed, the elastic-plastic seismic mitigation device was taken as the central buckle, and the influence of the elastic-plastic central buckle on the bridge seismic response was investigated, the seismic mitigation effectiveness of the bridge with different seismic mitigation systems was discussed. The results show that the elastic cable between the tower and deck is unfavorable to the seismic forces of the middle tower, the flexible central buckle is vulnerable to the suspension bridge under earthquake loads. The elastic-plastic device can be used as the suspension bridge central buckle. By installing the elastic-plastic central buckle, the longitudinal seismic displacement of deck can be effectively controlled and the seismic forces of the tower can be improved. When the combination of elastic cable and elastic-plastic central buckle was installing, the displacement of the suspension bridge is reduced more obviously, the adverse effect of the elastic cable on the middle tower can be mitigated. The seismic performance of the triple-tower suspension bridge can be effectively improved by the application of elastic-plastic central buckle.