Abstract: Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder caused by insulin deficiency and insulin resistance.Vitamin C (V_C) is an essential nutrient for human body. Vc is an antioxidant to protect cells from oxidative stress. Oxidative stress state played an important role in the occurrence and development of T2DM and its complications. Appropriate supplementation of V_C can reduce the risk of T2DM and complications. Recent studies has shown that V_C is closely related to the occurrence of T2DM and its complications. The evidence is that plasma V_C levels are generally low in patients with T2DM and inversely associated with the risk of T2DM. Supplementation of V_C in T2DM patients can improve insulin resistance and inflammation, and also reduce the risk of diabetic nephropathy and cardiovascular disease, but there is no significant improvement in diabetic periodontal disease. This paper summarizes the role of V_C in the occurrence and development of T2DM and its complications, with the purpose of providing reference for the prevention and treatment of T2DM.