The study will assess the changes in cognitive function, daily living skills, executive functions, behavioral and psychological symptoms. The primary measures of effectiveness include the change from baseline in the vascular dementia assessment scale cognitive subscale (V-ADAS-cog) and Alzheimer's disease cooperative study-clinical global impression of change (ADCS-CGIC). Secondary measures of effectiveness include the change from baseline in the Alzheimer's disease cooperative study-activities of daily living inventory (ADCS-ADL), mini-mental state examination (MMSE), clinical dementia rating scale (CDR), sum of boxes of CDR(CDR-sb), clock drawing task (CLOX), Chinese version of executive interview 25 (C-EXIT25) and neuropsychiatric inventory (NPI). Safety measures include physical examinations, vital signs, electrocardiography, laboratory tests, and adverse events records.