Abstract: Objective\ To study the effects of AngⅡ receptor antagonist losartan on HRV in essential hypertension patients. Methods\ After 2 w washout period,29 patients with essential mild to moderate hypertension received once daily losartan 50 mg～100 mg for 8 w. The 24 h ambulatory ECG were performed before and after 8 weeks treatment. Spectum of heart rate variability was analysed. Results\ After Losartan treatment ,SDNN were decreased,while rMSSD and PNN50 increased. In associaion with the increases in HF,the LF,VLF and LF/HF were decreased. There were significant differences before and after active treatment. Conclusion\ Losartan not only decreases blood pressure but also shows beneficial effect on HRV.