To determine the steel corrosion model of in-service reinforced concrete (RC) bridge more reasonably, the existing research literatures on steel corrosion were reviewed and compared and a revised steel corrosion model by considering the load effect and chlorine ion combining ability was developed. The model was used in study of in-service reinforced concrete bridge near coastal areas, and its validity was verified. The result shows that the model is more reasonable when compared with the traditional chloride diffusion models. It is practical to adopt the model for simulating materials deterioration and predicting structural service life.