Abstract: Objective To study the effect of folic acid(FA)on the expression of transforming growth factor β₁ (TGFβ₁) in myocardial cells of Homocysteine(HCY)mice,and to found out the measure to control cardiovascular disease.Methods Twenty four male Kunming mice were randomly divided into three groups:control group(0.1 ml Saline injected in abdominal cavity),HCY group and FA group(HCY 16μmol/kg.d injected in abdominal cavity);Intragastric adrninistration after 2h of abdominal cavity injection:0.1 ml saline in NS group and HCY group,folic acid 1.0μmol/kg·d in FA group.This was done for continous of 5 days.4 h After the last administration,the weight of body and heart were measured,routine paraffin section,the TGFβ₁ of cardiac muscle cell were measured with immunohistochemical method.The area of cardiac muscle cell were measured by HPIA-2000 image computer analyzer.Results The weight of heart and heart/body and the expression of TGFβ₁ in myocardial cells were significantly decreased(P<0.01,and P<0.05)in FA group than in HCY mice;The augmentation of myocardial cell area and lactic acid dehydrogerlase(LAD)in HCY mice were significantly decreased by folic acid (P<0.01).Conclusion As one of protective agent of the myocardial cell,the folic acid may decrease myocardial cells dam2 age in HC Y mice through adjusting the expression of T GFβ₁,and to preventheart disease.