Aim To investigate the therapeutic effect and mechanism of Huangqixianxiong capsule on isolated systolic hypertension in the elderly(EISH).Methods 100 patients were divided into Huangqixianxiong capsule group and control group in a random,double-blind and placebo control modality.50 patients in the Huangqixianxiong capsule group took Huangqixianxiong capsule and placebo of perindopril(acertil),while the other 50 patients in the control group took acertil and placebo of Huangqixianxiong capsule.Changes of clinical manifestation between pre-and post-treatment were observed by combined TCM and Western medicine syndrome,and the blood parameters were analyzed by molecular biology technology.Results Compared with the level before treatment,systolic blood pressure value were obviously decreased in both groups after 5 and 10 weeks treatment(p<0.01).The total depressurization curative effect rate in the Huangqixianxiong capsule group was 76%,versus 73% in the control group(p<0.05),and the total effective rate in symptoms and signs of traditional Chinese medicine were 92%,which was better than that in the control group.Lab test showed that the increase of blood nitric oxide synthase(NOS)activity and decrease of malonaldehyde(MDA),neuropeptide Y(NPY)and homocystein(Hcy)in the Huangqixianxiong capsule group were all superior than that in the control group(p<0.05).Conclusions Huangqixianxiong capsule has a better effect on EISH without apparent toxic and side effects,and the regulation of NOS,MDA,NPY and Hcy may be included in its mechanism of action.