Abstract: At present, chronic kidney disease (CKD) has become a major disease threatening human health around the world, and it is often complicated with serious cardiovascular events, such as hypertension, atherosclerosis, coronary artery disease, heart failure and so on. However, cardiovascular diseases (CVD) can also have a feedback and induce renal dysfunction. There is a causal relationship between CKD and CVD, which is the main reason for the increased risk of death in patients with CKD. In recent years, the relationship between intestinal flora and organs in health and disease has become a hot spot for scholars at home and abroad. Trimethylamine-n-oxide (TMAO), as a class of biologically active and water-soluble small molecule compounds mainly produced by intestinal flora, is involved in the occurrence and development of CKD and CVD by triggering a series of pathophysiological changes. Therefore, in order to further understand the clinical significance of intestinal metabolite TMAO in the treatment of cardio-renal diseases, this review will elaborate the important value of TMAO from the aspect of how TMAO participates in CKD and the etiology and mechanism of CVD.