Trimethylamine-N-oxide (TMAO) is produced through the conversion of the dietary compound choline, carnitine and betaine by intestinal microbiota. With the improvement of people's living standard, high-fat diet has increased the production of TMAO. Acting as a bridge, intestinal microbiota participates in metabolism, through which TMAO is produced and exerts harmful effect on human body. This review mainly focuses on the role of intestinal microbiota in the production of TMAO, the impact of TMAO on intestinal microbiota, as well as the effect of intestinal microbiota on the role of kidney and intestine in the "renal-intestinal axis" through TMAO. It explores the relationship between TMAO and kidney/intestine and diarrhea from the perspective of the "renal-intestinal axis", and is of great significance to reveal the impact of TMAO on the occurrence and development of related diseases through inflammatory mechanisms and oxidative stress processes.