Abstract: Four alkaloids were isolated from the total alkaloids of the twigs and leaves of Alstonia yunnanensis (Apocynaceae) by using silica gel, ODS, Sephadex LH-20, and HPLC chromatography. Structures were determined by physical, chemical and spectroscopic methods and identified as N₄-methylpseudoakuammigine (1), pseudoakuammigine (2), vinorine (3), picraline (4). Among them, compound 1 is a new monoterpenoid indole alkaloid.