Diabetes mellitus is a chronic endocrine/metabolism disease characterized by hyperglycemia arising from defects in insulin action, insulin secretion, or both. Diabetes mellitus is often complicated by visceral lesions, which can lead to serious complications and death. A variety of new agents are in development for the treatment of the disease. Astragalus polysaccharides are monomer components extracted from the Traditional Chinese Medicine, Huangqi (Radix Astragali Mongolici), which have been studied widely for treating diabetes mellitus with promising effects in recent years. This paper reviews recent advances in experimental studies on the effects of Astragalus polysaccharides in treating diabetes mellitus. The effects of Astragalus polysaccharides on the etiology and complication of diabetes mellitus including insulin resistance and secretion, diabetic neuropathy, diabetic retinopathy, diabetic cardiomyopathy, diabetic foot, and infection complicated by diabetes mellitus are discussed.