In this study, through experimental research and an investigation on large datasets of the durability parameters in ocean engineering, the values, ranges, and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed. Based on a modified theoretical model of chloride diffusion and the reliability theory, the service lives of concrete structures exposed to the splash, tidal, and underwater zones were calculated. Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed, and a cover thickness requirement was proposed. In addition, the effects of the different time-varying relationships of the boundary condition (C_s) and diffusion coefficient (D_f) on the service life were compared; the results showed that the time-varying relationships used in this study (i.e., C_s continuously increased and then remained stable, and D_f continuously decreased and then remained stable) were beneficial for the durability design of concrete structures in marine environment.