Aim To observe the effect of peroral folic acid in patients with coronary artery disease （CAD）. Methods Sixty patients with CAD were involved in the study, and were randomly divided into placebo and folic acid groups each with 30 patients. Backgrounds and levels of serum folic acid, homocysteine （Hcy）, malondialdehyde （MDA）, low density lipoprotein cholesterol （LDLC） and flow-mediated vasodilation （FMD） were measured, and the difference was detected. All patients were given medicines based on secondary prevention of CAD. Then patients were given 5 mg/d of folic acid or placebo orally respectively for 4 weeks until 8 weeks. After periods of treatments, indicators of the forementioned were measured and compared not only between the two groups, but also before and after treatments.