Objective: To explore the mechanism of Qiangpi Bujing Huayu Yizhi Capsule(QBHYC) in treatment of multi-infarct dementia(MID).Methods: The complex MID model was made by administration of Small Chengqi Decoction and injection of emboli into the internal carotid artery.The dementia rats were randomly divided into 4 groups,the sham operation group,the operation group,the Chinese materia medica group and the western medicine group.The activity of SOD and the content of MDA in the rats' plasma and brain were detected by photochemical methods,and the mechanism of the possible intervention effects of QBHYC was analyzed.Results: The activity of SOD in the Chinese materia medica group was significant increased,while the content of MDA of this group was attenuated,compared with that of the operation group and the western medicine group,it had highly significant difference(P