Vascular dementia (VaD) is a clinical syndrome of acquired intellectual and functional impairment that results from cerebrovascular diseases. SaiLuoTong capsule is a traditional Chinese medicine compound; it is composed of ginseng extract (the main composition: ginseng total saponins), ginkgo biloba extract (the main composition: YinXingTong ester) and safflower extract (the main composition: the west safflower total glycosides). The function of SaiLuoTong capsule is Yiqi Huoxue and Huayu Tongluo in Chinese traditional medicine theory. Pharmacodynamics studies showed that SaiLuoTong capsule can significantly improve neurological symptoms caused by focal cerebral ischemia in animals, and learning and memory ability in animal models of VaD. Based on these previous evidences, we conduct this study to assess the efficacy and safety of SaiLuoTong capsule in patients with mild to moderate VaD. This study is a phase 2 clinical trial of SaiLuoTong capsule for treatment of vascular dementia. The initial study is a 26-week, multicentre, randomized, double -blind, placebo-controlled study. Patients who complete the initial 26-week trial will be eligible to continue in a 26-week open-label extension study.