In order to study the influence of reinforcement ratio on the ductile seismic performance of reinforced concrete bridges, the reasonable value of main reinforcement ratio was subdivided in different fortification intensity. Taking reinforced concrete bridge as the research object, the relationship between vertical reinforcement ratio and pier ductility was studied by means of quasi-static model test and finite element numerical analysis, and the quantitative index of multi-stage performance level of typical piers was put forward. And the influence of different reinforcement ratio on the seismic performance of bridges in the harsh environment of chloride erosion was also explored, so as to provide reference suggestions for the range of reinforcement ratio of small and medium-span bridge piers in the earthquake area under chloride erosion environment. The results show that the restoring force model under chloride erosion can better reflect the degradation characteristics of stiffness, and the range of the optimal reinforcement ratio of piers is 1.11%~2.72%. When the acceleration is 0.30g, the damage index of piers can not be satisfied only from the point of view of reinforcement ratio. It is suggested that seismic isolation system should be used for seismic design, such as ductility system, the reinforcement ratio should not be less than 2.64%. The research results can provide reference for the revision of seismic code for small and medium-span continuous bridges.