Abstract: Mycosporine-like amino acids (MAAs) are water-soluble substances characterized by a cyclohexenone or cyclohexenimine chromophore conjugated with the nitrogen substituent of amino acids, having absorption maxima ranging from 310 to 360 nm. MAAs can be synthesized in fungi,marine heterotrophic bacterium, cyanobacteria, and eukaryotic algae, and accumulate in marine invertebrates, fish and a wide variety of other marine organisms. They are involved in the UV screening,osmotic and reproductive regulation and development protection. This review highlights the distribution and structure and physiological function of MAAs. Its biosynthesis and accumulation are also discussed.