Polysaccharides are a kind of biological macromolecule, which widely exists in plants, fungi, animals, microorganisms, and other organisms. Polysaccharides exhibit various biological activities such as immunological regulation, antioxidation, antitumor, antiinflammatory, regulating intestinal flora, and protecting liver. These biological activities depend on their structure and physicochemical properties including monosaccharide composition, molecular weight (Mw), spatial configuration, etc. However, biological activities of polysaccharides are hardly comparable to synthetic drugs due to their inherent physicochemical properties. Therefore, structural modification of polysaccharides is an effective way to enhance their biological activities and promote the presentation of bioactivity. At present, phosphorylation modification is a common chemical modification method, which can effectively improve the biological activities of polysaccharides. However, there are limited reports on the synthesis, structure identification, and biological activities of phosphorylated polysaccharides. In view of this, the synthesis methods, structure identification methods, and biological activities of phosphorylated polysaccharides are reviewed in this paper. The findings can provide useful guidance for the research, production, and application of phosphorylated polysaccharides in functional foods and therapeutic agents.