Abstract:Intestinal flora is a complex ecosystem which affects many aspects of human physiology, such as diet, disease development, drug metabolism, and immune system regulation. Ubiquitous in animals, plants, and microorganisms, polysaccharides have a variety of physiological activities. Intestinal flora interacts with polysaccharides and digests indigestible polysaccharides. Polysaccharides, which are an important energy source of intestinal flora, promote the proliferation of probiotics. Disorder of intestinal flora leads to the occurrence of diseases, and polysaccharides can alleviate the diseases by regulating intestinal flora. With the launch of Human Microbiome Project and the in-depth research on intestinal flora in China and abroad, relationship between polysaccharides and intestinal flora has been gradually elucidated. However, the relationship between intestinal flora and polysaccharide structure needs to be further explored. Therefore, this article summarized the interaction between polysaccharides and intestinal flora and the alleviation of diseases through regulating intestinal flora structure, and discussed the structure-activity relationship between polysaccharides and intestinal flora from the following aspects: molecular weight of polysaccharides, glycosidic bond, and monosaccharide composition. Moreover, we summed up the future research directions, hoping to provide a reference for further research on disease treatment.