As a traditional Chinese medicine compound, SaiLuoTong capsule is proven to have beneficial effects on learning and memory ability in animal models of vascular dementia (VaD). The study hypothesis is that SaiLuoTong capsule will be effective in the treatment of patients with VaD and will be well tolerated. The purpose of the study is to determine the efficacy and safety of SaiLuoTong capsule on patients with mild to moderate VaD. The outcome measures include general cognitive function, executive function, daily living skills, and mental behavior changes of symptoms in VaD patients.