In the course of screening Korean natural plants for acetylcholinesterase (AChE) inhibitory activity, we found that a methanolic extract of the leaves of Securinega suffruticosa showed significant inhibitory effects on AChE. Bioassay-guided fractionation of the methanolic extract resulted in the isolation of dihydrosecurinine, as a active principle. This compound inhibited AChE activity in a dose-dependent manner, and the $IC_{50}$ value of dihydrosecurinine was $18.9;{mu}g$.