This study aims to investigate the life-cycle seismic performance degradation behaviour of reinforced concrete (RC) girder bridges under chloride-induced corrosion. Based on the Duracrete model and existing research results, the time-dependent deterioration models for the mechanical properties of longitudinal reinforcement, transverse reinforcement, cover concrete, and core concrete are determined. A three-span RC continuous girder bridge is taken as an example, and its nonlinear analysis models corresponding to different characteristic time points are established by the OpenSees platform. Four analysis cases are investigated to study the effects of chloride-induced corrosion on the girder bridge's seismic capacity and seismic demand. Among these cases, one involves the omission of considering the deterioration of ultimate tensile strain of reinforcing steel, while the remaining three consider this deterioration using three diverse degradation models. The results show that: in the presence of chloride-induced corrosion, the degradation of the ultimate tensile strain of reinforcing steel manifests markedly more severe than the deterioration observed in its yield strength; the girder bridge suffers a more significant decrease in ultimate curvature, a greater increase in curvature demand, and a lower curvature demand-to-capacity ratio of pier when considering the deterioration of ultimate tensile strain of reinforcing steel; disregarding the degradation of the ultimate tensile strain of reinforcing steel would render the life-cycle seismic performance evaluation results of girder bridge structures unreliable and unsafe; additionally, the applicability of these three deterioration models varies, and there are significant differences in the degree of degradation of curvature demand-to-capacity ratio among these models. Therefore, the choice among these three models should be grounded in the research application scenario. As a result, it is necessary to consider the deterioration characteristics of the ultimate tensile strain of reinforcing steel in the time-dependent seismic performance evaluation of RC girder bridges.