Aim To observe the effect of tanshinone ⅡA on asymmetry dimethyl arginine and NO in aortic endothelial cells of diabetic rats. Methods The diabetic model rats was induced and its aortic endothelial cells were primary cultured by tissue patch and intervened with 0,25,50 mg/L Tanshinone ⅡA sulfonate for 6 h,12 h and 24 h.The contents of asymmetry dimethyl arginine and NO in cell culture were determined by ELISA method and nitrate reductase method,respectively. Results The inhibiting effect of Tanshinone ⅡA sulfonate on asymmetry dimethyl arginine was in a dose-and time-dependent manner.The difference between each group had statistical significance(P<0.05).The promoting effect of secretion of NO was parallel to the increase of concentration,and it reached the peak in 12 h(P<0.05).Conclusion Tanshinone ⅡA can decrease the secretion of asymmetry dimethyl arginine in aortic endothelial cells and promote the synthesis of NO.