Objective: To explore the therapeutic effect of Jiangya Capsules on senile simple systolic hypertention and its mechanisms. Methods: The patients were randomly divided into treatment group（n = 24） and control group （n = 23）. Treatment group was treated by Jiangya Capsules and mimetic drug of Nimodipine capsules

and control group was given Nimodipine capsules and the mimetic drug of Jiangya Capsules. Results: The total effective rate for decreasing blood pressure was 75. 00% in treatment group and 73. 91% in control group

with no significant difference between the two groups （P>0. 05）. The systolic pressure was improved in two groups after treatment of 4 and 8 weeks （P <0. 01）. Total effective rate for TCM syndromes in the treatment group was 91. 66%

better than that in control group （P< 0. 05）. The increase of serum nitric oxide synthase （NOS）

and the decrease of malondialdehyde （MDA）

plasma neuropeptide Y（NPY） and homocysteine （Hcy） in treatment group were better than in control group （P<0. 05 or P<0. 01）. Conclusion: Jiangyan Capsules has a better therapeutic effect on senile simple systolic hyertention with no obvious toxic-side effects. Regulation of serum NOS activity and MDA level

and plasma NPY and Hcy contents are possiply some aspects of the mechanisms.