Abstract: Fucoidin is a kind of polysaccharide rich in sulfuric,which widely found in brown algae. Due to its extensive biological activities,such as anti-oxidation,immunity enhancement and anticancer,it has gradually become the focus of current research. The molecular polymerization of natural fucoidan was in high degree,which limits its application in related fields. With the deepening of research,the effect of structure and the different sources of fucoidin on their bioactivity have become a new research direction. In our study,the effect of the structure of fucoidan on its biological activity,which is anti-oxidation,anti-bacteria,immunity enhancement and tumor suppression were highlighted. In addition,the challenges of fucoidan research were also analyzed,which provides idears for the fucoidan application and science research.