As the technology of seawater desalination develops very fast in recent years, it has become an effective way to solve the problem of freshwater shortage. However, this may cause many problems, such as land occupation, noisy pollution, environmental issues caused by energy consumption, discharge of brine, higher temperature seawater and chemicals. In this paper, the progress of seawater desalination all over the world was described. The impacts of seawater desalination on marine environment was reviewed, especially the impacts on seawater quality and marine organisms of brine discharge with high temperature, high salinity, and chemical pollutants. Countermeasures are proposed to prevent or decrease the impacts mentioned above.