Objective To observe the therapeutic effect and mechanism of the aqueous extract of ephedra sinica on brain damage after subarachnoid hemorrhage(SAH)in rats.Methods Totally 50 rats of Sprague-Dawley were randomly divided into control group,model group and three groups treated with different concentrations(4,12,36 mg/kg).The changes of the cerebral water content,malondialdehyde(MDA),glutathione peroxidase(GSH-Px)and hydroxy radical of brain tissue were recorded,and he-matoxylin-eosin(HE)staining was used to test the subarachnoid haemorrhagia and oedema,and immunohistochemistry and western blot were carried out to assay the expression of complement C3 in brains of different animal in different group 3d after operation. Results On the postoperative 3 days,compared with the model group,the content of MDA、GSH-Px activity and hydroxyl radical of 12、36 mg/kg treatment groups significantly reduced(P <0.01 ),the content of MDA of 4 mg/kg treatment group not change (P >0.05),but GSH-Px activity and inhibition of hydroxyl radical significantly reduced(P <0.01),and the cerebral water content of 12,36 mg/kg groups were obviously lower compared with model group.The expression of complement C3 was significantly lower on 36 mg/kg treatment group and edema reduced.Conclusion The aqueous extract of ephedra could significantly inhibit the activity of complement C3,prevent the production of MDA、GSH-Px and hydroxyl radical,reduce the severity of cerebral edema and the in-flammatory response,which has a better therapeutic effect SAH animals.