Abstract: AIMTo study on the anticholinesterase active constituents of the rhizoma of Corydalis decumbens. METHODSVarious chromatography techniques were used to isolate and purify the chemical constituents. Their structures were elucidated by UV, IR, MS, ¹HNMR and ₁₃CNMR spectral analyses. Their anticholinesterase activity was measured with Ellman method. RESULTSFive compounds were identified as tetrahydropalmatine (I), protopine (II), bicuculine (III), sculerine (IV) and dehydrocorydaline (V). Compounds II and III possessed the action of anticholinesterase activity. CONCLUSIONProtopine (II) is the one of main anticholinesterase active constituents of the rhizoma of Corydalis decumbens.