The number of patients currently suffering from Alzheimer disease（ AD） has grown exponentially. However the pathogenesis of AD is still unknown， and the current treatment is only palliative. Some studies have found that patients with type 2 diabetes have a morbidity of AD. About three-quarters of AD patients have type 2 diabetes， suggesting that diabetes may be associated with AD. Current studies have found that there are many factors linking diabetes with AD， such as Aβ， tau protein， synaptic damage， oxidative stress， advanced glycation end products（ AGEs） production and immune system dysfunction. This review focuses on the molecular mechanism of AD induced by diabetes mellitus through the above links.