Abstract: Purpose\ To evaluate the effects of benazepri1 hydrochloride on heart rate variability（HRV） in 21 patients with mild to moderate essential hypertension.\ Methods\ 24 hours ambulatory ECG was used for detecting of HRV.\ Results\ Angiotensin converting enzyme inhibitors(benazepril hydrochloride l0～20 mg once daily for 8 weeks（\%n\%=21） reduced blood pressure（froml 53/102 to 139/93 mmHg） as well as standard deviation of normal RR intervals（SDNN）.\ While the standard deviation of 5 minute mean RR intervals（SDANN）,the square root of the mean of squared difference between adjacent normal RR interval（RMSSD） and highfrequency（HF） components of power spectrum density were increased. Total frequency（TF）,low frequency（LF） and high/low frequency ratio were markly reduced after taking 10～20 mg of benazepril hydrochloride.\ Conclusion\ It thus suggests benazepril hydrochloride therapy can significantly increase the heart rate variability of patients with essential hypertension.