[ ] Objectives: To investigate the change in endothelium dependent vasodilation function in active rheumatoid arthritis(RA) patients without clinical manifestations of cardiovascular disease. Methods: Consecutive 45 active RA inpatients without clinical manifestations of cardiovascular disease and 45 age- and sex-matched healthy subjects were enrolled. Arterial intima media thickness(IMT),hemodynamic parameters of brachial arteries were tested by ultrasound ,in addition , Endothelial dependent flow － mediated dilation (FMD) of brachial artery was measured. Results: Compared with control groups, the IMT and hemodynamic parameters had no statistical significance in RA group(P>0.05),but FMD of brachial artery with rheumatoid arthritis were reduced(5.09±2.71% vs11.26±5.66%, P<0.001).Conclusions: Endothelial dysfunctionS occur in active RA patients without clinical manifestations of cardiovascular disease ,before morphological features of blood vessel walls and hemodynamics were changed.