Based on several design cases of nuclear power plants in China, this paper expounds the the function of flood protection, intake and outlet and heavy-cargo unloading and transportation undertaken by the marine engineering structures of nuclear power plants, analyzes the relationships among flood protection, site elevation and revetment elevation design; the advantage, disadvantage and adaptability of different intake and outlet types, the common general layout of intake-outlet structures and water safety, warm water discharge, tide, sand, waves and other factors considered; as well as factors in the general layout of heavy cargo wharf.