Structural life-cycle seismic performance design and evaluation methods based on the life-cycle theory has become a hot research subject commonly concerned in bridge structural engineering in recent years. This paper investigates the life-cycle seismic performance of offshore reinforced concrete bridge structures considering the chlorine ions corrosion effect, a rebar corrosion degree formula based on the time-varying corrosion current density is put forward combining with the chloride ions corrosion models for the reinforced concrete structures. An offshore bridge structure exposed to the attack of chlorine ions is taken as an example, considering the degradation of the diameter and mechanical properties of the bridge pier longitudinal reinforcement and the performance degradation of the concrete, Pushover analysis and incremental dynamic analysis are performed at different life-cycle stage of the bridge, finally, the life-cycle seismic performance of the bridge is evaluated through seismic fragility analysis. The results show that as the chloride ions corrosion effect is processed, the seismic capacity of the bridge is reduced, the seismic demand under earthquake excitations are increased and the probability to reach every limit damage state is increased. This paper evaluates the life-cycle seismic performance of bridge structures, which can provide support for the bridge structural life-cycle seismic performance design method.