Abstract: As one of the most common microvascular complications of diabetes,diabetic kidney disease(DKD)is one of the major causes of end-stage renal disease. Complement system participates in both innate and adaptive immunities of human body. Three pathways of complement system intercross between complements C3 and C5 and complement C3 occupies a central position in complement system. This review summarized the possible mechanisms of complement C3 involved in the pathogenesis and progression of DKD.