Copper alloys have good resistance to seawater corrosion and marine biofouling, and are widely used in marine engineering. Therefore, the research on the corrosion behavior and protection technology of copper alloys in seawater is particularly important for the development of marine engineering and marine resources, and the improvement of marine economic benefits. In the natural seawater environment, the factors that affect the corrosion of copper alloys include: the type of copper alloys, different sea areas, seawater velocity, pH value, and microorganisms. In order to improve the corrosion resistance of copper alloys and prolong their service life in seawater, the main protective measures adopted are: electrochemical protection, paint, surface coatings, corrosion inhibitors, and so on. In this paper, the corrosion mechanism of coppernickel alloys in seawater is summarized firstly, and then the main influencing factors of coppernickel alloy corrosion in seawater and the new research progress of protection technology are summarized emphatically. Finally, the research and development trends of seawater corrosion and protection of copper alloys are prospected.