Abstract: The sea cucumber is an invertebrate with significant economic value and is extensively consumed as a tonic food in Asian countries due to its high nutritional value. Sea cucumber polysaccharides, important bioactive substances found in sea cucumbers, exhibit diverse biological activities, including anticoagulant, antitumor, antioxidant, immunomodulatory, and insulin resistance-alleviating activities. Sea cucumber polysaccharides include fucosylated chondroitin sulfate (FCS) and fucoidan (FUC). FCS exists in the body wall of sea cucumbers and has a backbone structure similar to that of mammalian chondroitin sulfate. Compared with sea cucumber FCS, sea cucumber FUC has a simpler chemical structure and is a linear polysaccharide consisting of only α-L-fucose and sulfate groups. It has been shown that the structural properties of sea cucumber polysaccharides (molecular mass, sulfated fucose branches, sulfate group content and sulfation patterns) have a large influence on their biological activities. At present, there are many studies on the biological activities of sea cucumber polysaccharides, but systematic research and analysis on their chemical structures are still lacking. This review focuses on outlining the chemical structures, biological activities, action mechanisms and structure-activity relationship of sea cucumber polysaccharides, with a view to providing a reference for further research and application of sea cucumber polysaccharides.

Key words: sea cucumber polysaccharides; chemical structure; biological activity; structure-activity relationship; mechanism of action