Vascular cognitive impairment (VCI) is a progressive cognitive impairment caused by cerebrovascular disease or vascular risk factors. It is the second common type of cognitive impairment after Alzheimer's disease. VCI can be caused by a variety of signal and metabolic pathways. Its core mechanism is that cerebrovascular disease destroys the neurovascular unit composed of neurons, glial cells, and cerebrovascular endothelial cells. This article summarizes and discusses the known mechanisms of VCI, in order to deepen the understanding of the molecular pathological process of VCI and provide ideas for its prevention and treatment.