A huperzine A compound is provided. The huperzine A compound has following formula: wherein X comprises O or S, Y comprises --O--, --S--, --CH(R.sub.4)--, --C(R.sub.4)(R.sub.5)--, --C(R.sub.4).dbd.C(R.sub.5)--, --C.ident.C--, --NH-- or --N(R.sub.4)--, n is 0, 1 or 2, R.sub.3 is C(.dbd.X)--(Y).sub.n-R.sub.1 provided that R.sub.2 is H or R.sub.2 and R.sub.3 are combined to form .dbd.CH--Ar, wherein R.sub.1, R.sub.4 and R.sub.5 independently comprise hydrogen, C.sub.1-C.sub.32 alkyl, C.sub.1-C.sub.32 alkenyl, C.sub.1-C.sub.32 alkynyl, C.sub.1-C.sub.32 aryl or C.sub.1-C.sub.32 heteroaryl, in which alkyl, alkenyl, alkynyl, aryl or heteroaryl with one or more substituents comprising halogen, hydroxyl, alkoxy, aryloxyl, amino, alkylamino, arylamino, dialkylamino, diarylamino, imino, alkylimino, arylimino, acylamido, diacylamido, acylimido, cyano, nitro, mercapto, carbamido, carbamoyl, carboxyl, thioureido, thiocyanato, sulfonamido, thio, sulfonyl or sulfinyl, and Ar comprises aryl or heteroaryl.