To study chemical constituents of the root of Alstonia yunnanensis Diels.Five compounds were obtained by means of silica column chromatography,gelchromatography and recrystallization.Based on the modern spectral analysis methods such as mass spectrometry (MS) and nuclear magnetic resonance (NMR),the structures of these compounds were identified as 17-amino-acetoxy-sarpagane (1),tetrahydroalstonine (2),vinorine (3),17-acetylsarpagine (4) and Vellosimine (5),respectively.Compound 1 was a newindole alkaloid.Compounds 3 and 5 showed cytotoxic activity against tumor cells.