Abstract: As an important renewable marine biological resource, the high-value utilization of seaweed is a hot spot in current research and industry. The main nutritional components (e.g., proteins, lipids, polysaccharides, minerals, vitamins) and biological activities of seaweed were reviewed in this paper, with a focus on its processing technology and the latest progress and application prospects in many fields. In the food industry, the seaweed has been developed into a variety of new healthy foods, and its extracts could be used as the natural additives. In the field of health industry, its active ingredients showed great potential in the development of functional foods and drugs, which was of great significance for the prevention of chronic diseases. In the cosmetics industry, the seaweed extracts were the important natural raw material for skin care. In addition, the seaweed-based biomaterials also showed unique advantages in environmentally degradable materials and high-end biomedical materials. Although the prospect was broad, the high-value utilization of seaweed still faced multiple challenges such as the resource shortage, immature technology and market competition. Therefore, the future research should focus on the key directions such as the efficient utilization of resources, advances in processing technology and intelligent upgrading, in-depth analysis of activity mechanism and industrial transformation, so as to systematically promote the high-value development and sustainable utilization of seaweed resources.