Functional oligosaccharides refer to short-chain sugar molecules with specific biological activities or functions, usually composed of 2 to 1 monosaccharide units. They play a variety of important roles in organisms and are widely used in food, nutrition, health care, medicine and other fields. Functional oligosaccharides play an important role in multiple biological processes. They not only have health benefits such as prebiotics, immunomodulation, anti-inflammatory and antioxidant, but also provide a variety of potential applications in medicine, nutrition, food industry and other fields.