Abstract: A finite element model was built for a curve bridge with an unseating-prevention device. The collision effect of the curved bridge under rare earthquake was studied and the dynamic response mechanism was discussed based on this finite element mod-el. The influence of expansion joint setting on the dynamic characteristics of the curved bridge was analyzed. It is found that the spec-tral characteristics of seismic waves have significant effect on the collision effect, and the collision frequency between the adjacent frames increases under far field earthquake, while the collision force decreases. When the expansion joint increases, the effect on the axial force of the unseating-prevention device weakens, the collision force increases, but the collision times are basically unchanged. The expansion joint significantly affects the plastic development of the pier bottom. The curvature ductility demand reduces with decreasing expansion joint, and more than 62.5% drops compared that without the expansion joint.