Abstract: Seventeen compounds were isolated from the ethyl acetate extract of the tubers of dry Alisma plantago-aquatica by silica gel, Sephadex LH-20 and high performance liquid chromatography. All of them were identified as the prototerpene triterpenoids by the analysis of mass spectrometry and nuclear magnetic resonance spectroscopy. Compounds 1 and 2 are the new compounds. Among of them, 16 compounds were screened for α-glucosidase inhibitory activity, however, none of them was active.