The invention discloses application of L-arabinose in preparing medicines or health-care products for preventing or treating metabolic syndrome, and in particular application of L-arabinose in preparing medicines or health-care products for simultaneously reducing total cholesterol, triglyceride, fasting blood-glucose, blood pressure, waistline and weight, blood uric acid and glutamic-pyruvic transaminase of human body. The applicant discovers that for adults, in a taking dosage range of 10-20g/person/day, total cholesterol, triglyceride, fasting blood-glucose, blood pressure, waistline and weight, blood uric acid and glutamic-pyruvic transaminase of human body can be simultaneously reduced clinically. Not only is functions of the body not damaged, but also digestion and absorption of proteins and vitamins are not affected while the indexes are simultaneously reduced, so that the purpose of improving the functions of the body and preventing and treating metabolic syndrome is realized.