Abstract: With the upgrading of science technology and the change of consumer's concept, the research of the large-scale marine algae is becoming more and more intensive, and the seaweed polysaccharide as an important component of the seaweed is the focus and key point of the research. In this paper, methods of water extraction, alcohol extraction, acid alkali extraction, enzyme extraction, ultrasonic assisted extraction and microwave assisted extraction of polysaccharides from marine algae were reviewed, and the immune regulation, anti-tumor, antiviral, hypoglycemic, blood lipid and antioxidant activity of marine algal polysaccharide were detailed described. The paper introduced the application of seaweed polysaccharides in biological medicine, food and cosmetics fields, and put forward the future focus direction of research, in order to provide a reference for the development and utilization of high value seaweed.