Yam is an important medicinal and edible plant, rich in various bioactive ingredients such as polysaccharides, allantoin and saponins. Yam polysaccharides have various functional properties like antioxidant, anti-aging, anti-tumor, immunoregulatory, hypoglycemic, and hypolipidemic effect, and are promising for application in the development of health foods and drugs. The structure of yam polysaccharides is complex, and the monosaccharide composition, molecular mass, glycoside and glycochain structure have great influence on the biological activity of yam polysaccharides. Therefore, exploring the structural characteristics of yam polysaccharides is of great significance to understand their bioactive mechanism. In this paper, the structural characteristics and bioactive mechanism of yam polysaccharides are introduced, and the relationship between their structural characteristics and biological activity is also discussed, in order to provide theoretical support for the application of yam in the fields of health foods and drugs.