Abstract: Alginate oligosaccharides could be obtained by chemical and enzymatic hydrolysis of alginate. It has lower molecular weight,better water solubility and higher absorption than alginate. It also possesses lots of biological activities,including antioxidant activity,anti- hypersensitive activity and anti- allergy property. Chemical modification of alginate oligosaccharides serves a tool to improve its physical properties and physiological activities,thus expanding their uses in food and pharmaceutical areas. However,reviews are limited on biological activities of alginate oligosaccharides and their derivatization.Therefore,in this review,the present research status of alginate oligosaccharides and their derivatization was highly summarized. Besides,the prospect of alginate oligosaccharides and their derivatization was proposed.