Alzheimer′s disease（AD）is a neurodegenerative disease in the central nerve system with insid⁃ ious onset and progressive memory loss，cognitive decline，psychotic and behavioral changes. AD has been mainly considered as a grey matter disorder. Nevertheless，recent evidence suggests that myelin impairment may play an important role in AD pathology. It has also been found that myelin pathology may even precede Aβ and tau patholo⁃ gies. We summarized the evidence of white matter abnormalities from pathology and imaging studies，the role of my⁃ elin in cognition and possible mechanism of myelin damage in AD. Myelin damage combined withother pathological injury contributes to the process of AD. Many factors，such as aging，gene，Aβ⁃mediated toxicity and tau，isch⁃ emic injury also cause myelin breakdown. Therefore，elucidating the exact mechanisms leading to the disruption of myelin in AD may help a better understanding of AD，and thereby its prevention and treatment.