Backgrounds: The effect of folic acid on cardiac myocyte apoptosis secondary to diabetes is unknown.Methods: Diabetic rats were divided into diabetic control (DC, n=11), low-dose (LDF, 0.4mg/kg/day, n=12) and high-dose (HDF, 1.2mg/kg/day, n=12) folic acid groups. Non-diabetic rats (n=11) were used as the normal control (NC).Results: After 11 weeks of treatment, compared with the NC group, the DC group showed a reduced blood levels of reactive oxygen species (ROS, P<0.01). The rate of cardiac myocyte apoptosis in the diabetic control group was also greater than in the non-diabetic control group (P<0.01). In folic acid-treated rats, the blood levels of ROS was higher than in the diabetic control group (P<0.05). There was a dose-dependent reduction in the rate of cardiac myocyte apoptosis in the folic acid groups (P<0.01), and this was accompanied by an increased level of anti-apoptotic protein Bcl-2 and decreased level of pro-apoptotic protein Bax and Fas (P<0.01).Conclusions: Dietary folic acid supplementation diminishes the cardiac myocyte apoptosis in streptozotocin-induced diabetes. The apoptosis suppression is accompanied by an increase in the expression of Bcl-2 and a decrease in Bax and Fas.