The elderly is susceptible to diabetes mellitus and senile dementia, which is also called Alzheimer’s disease (AD). Epidemiological studies showed that there are so much in common between diabetes and AD in the elderly. With population aging, these 2 diseases severely threaten the elderly’s health. In- depth understanding of the relationship between diabetes and AD is of great significance to further elucidating the pathogenesis of AD and seeking for new therapeutic approaches. This article reviewed the relationship between senile diabetes and dementia in order to increase the awareness of the above 2 diseases for clinical physicians.