The invention provides an application of a Rac1 activity inhibitor in preparation of drugs for treating an Alzheimer
disease. The Rac1 activity inhibitor can be: at least one of EHop-016, CS7171, JKF-034, Secramine, AZD0530, NSC23766, MBQ-167, AZA1, AZA197, Compound 19,
ZINC08010136,
ZINC07949036, 69391, 1A-116, ITX3, ITX1, CPYPP, GGTase1inhibitor(P61A6, Statins), EHT1864, Compound 1, MLS000532223, R-
Ketorolac, OSU-3012, FL172, FRAX597, Phox-11, 187-1 and Wiskostatin. The invention protects the discovery of a mechanism for treating AD by inhibiting the activity of a forgetting regulatory molecule Rac1, and protects the application of a
small molecule compound capable of inhibiting Rac1 activity in treating AD.