Mechanics of performance degradation for harbor engineering under stress and chloride ions is discussed. The safety of structure is described by bearing capacity while the applicability is described by stiffness and longitudinal crack. The model for corrosion rate of reinforcement for RC port structures is proposed after considering the effects of stress intensity and duration and chloride ions on structure performance. The deterioration model of bearing capacity, development model of longitudinal crack and degradation model of stiffness characterized by corrosion rate of reinforcement are established based on the theoretical analysis on multiple factors and lab corrosion experiments.