Abstract: Metabolic syndrome is a group of clinical syndromes, including obesity, dyslipidemia, hypertension, hyperuricemia, hyperglycemia and insulin resistance. These syndromes are critical risk factors for cardiovascular disease and diabetes. Recent studies indicate that L-carnitine exhibits potential improvement effects on metabolic syndrome. In the current study, the sources of L-carnitine for human and the effects and mechanisms of L-carnitine on the major components of metabolic syndrome, such as obesity and dyslipidemia, etc were summarized. The potential health risk of L-carnitine by serving as a dietary precursor for trimethylamine N-oxide was also discussed. This study provides theoretical basis and references for the treatment of metabolic syndrome and the rational dietary supplement and utilization of L-carnitine.