Cardiovascular and cerebrovascular diseases caused by atherosclerosis (AS) are a kind of diseases that seriously damage human health. In recent years, it has been found that trimethylamine oxide (TMAO), a metabolite of intestinal flora, plays an important role in the pathogenesis of AS: inhibition of cholesterol reverse transport, up regulation of scavenger receptor expression, promotion of foam cell formation, reduction of bile acid pools, enhancement of platelet reactivity, increase of thrombosis risk, damage of vascular endothelium and promotion of inflammatory response. More and more scholars have paid attention to the specific effect and exact mechanism of TMAO on AS. This paper reviews the general characteristics of TMAO, the role of TMAO in the development of AS, and the latest research progress in the prevention and treatment of AS by intervening with TMAO.