Abstract: Going with the social olden，the incidence rate of Alzheimer′s disease increase evidently，the treatment become more important. More and more studies show that estrogen can prevent Alzheimer′s disease. Estrogen can lower brain Aβ content, suppress tau phosphorylation, improve the acetylcholinesterase activity, regulate apolipoprotein-E expression, increase cerebral blood, decrease inflammation and maintain the balance of calcium. This review recapitulates the important role of estrogen in the mechanism of the prevention of AD from the angle of the pathogenesis of AD，in order to provide basis for clinical treatment.

Key words: Alzheimer disease, Estradiol, Amyloid beta-protein precursor, Tau proteins, Therapy