Nostoc sphaeroides kützing is a freshwater wild blue algae that has gained significant attention due to its unique nutritional value and multiple biological activities. Nostoc sphaeroides kützing contains a variety of nutritional components, including polysaccharides, proteins, amino acids, fatty acids, vitamins, and mineral elements. It has demonstrated antibacterial, anticancer, lipid-lowering, and antioxidant effects. This article systematically reviews the extraction methods, structural characteristics, biological activities, and applications of Nostoc sphaeroides kützing polysaccharides, and provides an outlook on its future research directions.