Diabetes is a metabolic disease mainly characterized by hyperglycemia due to inadequate insulin secretion. And persistent hyperglycemia can cause chronic damage or dysfunction of eyes， kidneys， heart， blood vessels and nerves. Polysaccharides are high molecular carbohydrates polymerized by glycosidic bonds from more than 10 monosaccharide molecules of the same or different types. They have the advantages of wide sources， high safety and low toxic and so on. As one of the important effective components of traditional Chinese medicine， polysaccharides have biological activities such as immune regulation， anti-oxidation， anti-tumor， lowering blood sugar and so on. The structure is directly related to biological activities， and the advanced structure of polysaccharides is based on the primary structure. Exploring the primary structure of polysaccharides is the key task of lowering blood sugar and improving diabetic complications. This paper summarizes the monosaccharide composition of the primary structure of Chinese medicine polysaccharides， and the mechanism of Chinese medicine polysaccharides improving diabetes is emphasized by increasing the secretion and release of insulin， increasing the islet β cell number， upregulating insulin receptor level， improving glucose and lipid metabolism， inhibiting inflammatory response， improving oxidative stress and regulating phosphatidylinositol-3-kinase（PI3K）/protein kinase B （Akt）， mitogen activated protein kinase， cyclic adenosine monophosphate（cAMP）/protein kinase A（PKA） and adenosine monophosphate activated protein kinase（AMPK） signaling pathways. At the same time， we also summarized the prevention and treatment of Chinese medicine polysaccharides in diabetic nephropathy， diabetic cardiomyopathy， diabetic ophthalmopathy and diabetic peripheral neuropathy， in order to provide a theoretical basis for new drug development and clinical application of Chinese medicine polysaccharides in the intervention of diabetes and its complications.