Epidemiological studies have shown that the risk of Alzheimer’s disease （AD）in postmenopausal women is much higher than that in men. Numerous clinical trials have indicated that decreased level of brain-derived estrogen in women is related to the risk of AD. This review focuses on the synthesis，metabolism and action mechanisms of estrogen（especially brain-derived estrogen），the role of brain estrogen receptors（ERs），brain-derived estrogen in the regulation of cognitive function and brain-derived estrogen dysfunction in the progression of AD.