Abstract: To study the damage evolution of corroded coastal bridge piers under cross-shaped bidirectional loads, two reinforced concrete (RC) pier specimens with the same dimensions and reinforcement were designed, and one of them was electrochemically corroded. The two specimens were tested quasi-statically under cross-shaped bidirectional loads. The influence of corrosion on the hysteretic behavior and stiffness degradation of the piers was analyzed. Based on the test phenomena and an improved Park-Ang dual-parameter damage model which considers the corrosion and loading path, the damage evolution processes of the piers were studied. The results show that, compared with the uncorroded pier, the ultimate strength of the pier with a corrosion rate of 24.15% was reduced by 28.74% and the cumulative energy consumption was reduced by 55.74%. The corrosion obviously accelerated the bidirectional seismic damage process of the pier. The contribution of the deformation to the dual-parameter damage indexes of the uncorroded and corroded piers first decreased and then increased slowly with the increase of the displacement. Combined with the damage index range proposed by Niu and others, the improved Park-Ang model can reasonably quantify the damage state of the piers and provides reference for the bidirectional seismic damage analysis of corroded coastal piers.