Objective To observe the clinical effect of Yinian Jiangya Yin（Decoction for prolonging life and lowering blood pressure） on early primary hypertension patients and to explore its functional mechanism on vascular endothelial cells.Methods Totally 79 patients with early primary hypertension belonging to the TCM syndrome of phlegm and blood stasis in meridians and hyperactivity of liver yang were randomized into a treatment group（n=40） and a control group（n=39）.The treatment group was treated with Yinian Jiangya Yin while the control group treated with Tianma Gouteng Yin（Gastrodia-Uncaria Decoction）.The changes in TCM syndrome scores and blood pressure after treatment were observed and the serum nitrogen oxide（NO） and endothelin（ET） were measured after treatment.Results Compared with the control group

the significant difference existed in the scores of TCM syndrome and the effect on lowering blood pressure in the treatment group（P<0.05）.After treatment

the significant difference existed in ET and NO of two groups（P<0.05）.Conclusion Yinian Jiangya Yin is effective in promoting the TCM symptoms and lowering blood pressure.This may relate to its function of regulating ET and NO to restore the endothelium-dependent vasodilation.