In the marine environment, salinity is one of the key factors affecting the growth and survival, development, and reproduction of shellfish, and their life activities are constantly influenced by the changes of salinity in the local marine environment. Research on the mechanisms of adaptation to salinity stress in marine shellfish has been an ongoing concern of scholars, and a large number of studies have shown that salinity stress could affect the biological processes such as growth and survival, osmotic adjustment, energy metabolism, and immune response of marine shellfish. In recent years, following with the development and application of genomic and transcriptomic technologies, more and more studies have been conducted to explore the mechanisms of marine shellfish adaptation to salinity stress at the molecular level. Therefore, this paper focuses on osmotic regulation, energy metabolism regulation, immune response, transcriptome and genome on the research of adaptation mechanisms of marine shellfish to salinity stress, and then proposes the development potential of euryhaline shellfish in the field of saline alkali water. It can provide theoretical reference for the genetic breeding and healthy culture of marine shellfish.