Trimethylamine oxide (TMAO) is a product which is formed by the metabolism of choline and other substances depending on the intestinal microflora. In recent years, studies at home and abroad have found that TMAO plays an important role in the occurrence and development of atherosclerosis (As). TMAO promotes As by mediating inflammatory signals and gene expression in vascular endothelial cells, increasing thrombosis risk, increasing scavenger receptor and promoting foam cell formation, influencing cholesterol transport pathways and metabolic pathways. This paper summarizes the related literatures in recent years, and finds that by controlling diet, regulating intestinal flora, inhibiting trimethylamine precursor metabolism, inhibiting flavin monooxygenase activity, TMAO level in blood circulation can be reduced and As progress can be prevented.