Coronary bypass grafting (CBG) is the most effective method of treating coronary artery disease and venae saphena magna is commonly used as vein graft for surgical revascularization; however, the incidence of vein graft restenosis is more than 60% in ten years after CBG, which threatens the prognosis and long-term survival of the patients. The vein graft restenosis has multiple factors and levels, including de-endothelialization, thrombosis, re-endothelialization and arterialization of vein graft in the early stage, intimal hyperplasia in the middle stage, and atherosclerosis and plaque rupture in the late stage. This review summarized the latest researches of the mechanisms of vein graft restenosis after coronary bypass grafting and discussed the prevention methods.