Objective: To study the relationship between the activity changes of angiotensin Ⅱ (AngⅡ) in plasma,cerebrospinal fluid (CSF) and the pathophysiology of vascular dementia (VD) on the one hand and the therapeutic effects of ligustrazine (LIG) on VD and its mechanisms on the other hand. Methods: Case grouping: VD group with 50 cases (26 VD patients treated with LIG and 24 with Ginaton); cerebral infarction (CI) group with 62 cases (routine therapy was given) and control group (without organic disease in central nervous system) with 26 cases. Investigation method: To test cognitive function by Mini-Mental State Examination (MMSE), Functional Activities Questionnaire (FAQ), Hachinski Ischemic Scale (HIS) and P300 peak latency (P300PL). To measure the concentration of AngⅡ by radioimmunoassay(RIA) technology. Results: As compared with CI recovery phase or with control group, AngⅡ levels in CSF were markedly increased in VD group(P＜0.01), MMSE scores was significantly lowered (P＜0.01), P300PL was markedly prolonged (P＜0.01). In VD group, after treatment with LIG or Ginaton, levels of AngⅡ in plasma or CSF were markedly lowered (P＜0.01). The MMSE scores was significantly increased (P＜0.05), P300PL was markedly shortened (P＜0.01). After treatment, no significant difference was found between LIG and Ginaton therapeutic subgroups (P＞0.05). Conclusion: AngⅡ activity changes plays an important role in pathophysiological process of VD. LIG can improve cognitive function in VD. It may be correlated with improving of the disorders of AngⅡ in central nervous system.