Complement system is a reaction system comprising 35 proteins with enzyme activity common in serum,tissue fluid and cell membrane. It plays an important role in anti-infection. Abnormal complement activation is involved in incidence and progression of many inflammatory diseases. The complement is activated through typical,alternative and agglutinin pathways. Following cardiovascular stent implantation,the vessel endothelium of patients with coronary atherosclerotic heart disease is damaged; serum complement C3 could enter the arterial wall to damage arterial cells to enhance the permeability release antigenic components of vessel wall,and induce antibody production. The fixing immune complex is formed and induces platelet aggregation,attachment or lipidoses. Although humoral immunity becomes accentuated following cardiovascular stent implantation,the capability to resist microorganism is reduced,which stimulates self-protection of C3,aggravates inflammation,increases circulation complex,activates complement system and aggravates endothelial injury. C3 plays an essential role in occurrence and development of ischemic cardiovascular disease,and is an important cause for restenosis and thrombosis following cardiovascular stent implantation.