The present invention discloses an application of ilexgenin O in a preparation of a medicament for preventing and treating senile dementia. Alzheimer's disease is a disease mainly characterized by primary and progressive degenerative diseases of the central nervous system with clinical manifestation of irreversible deterioration of cognitive and memory functions, mainly due to the neuron damage caused by excessive Ap deposits in the brain. The present invention finds that ilexgenin O can prevent nerve cell damage caused by Ap, and thus has the prospect of being developed into an anti-senile dementia drug.
