A pharmaceutical composition for preventing and treating senile dementia and a preparation method therefor. The active ingredients of the pharmaceutical composition are prepared from the following raw materials in weight part: 20 to 50 parts of epimedium and 15 to 55 parts of tuckahoe； or 20 to 50 parts of epimedium, 15 to 55 parts of tuckahoe and 10 to 55 parts of acanthopanax； or 20 to 50 parts of epimedium, 15 to 50 parts of tuckahoe, 15 to 50 parts of acanthopanax, and 6 to 15 parts of rhizoma anemarrhenae.
