Abstract: Twenty compounds were isolated from the twigs and leaves of the 95% ethanol extract of Miliusa tenuistipitata W. T. Wang by various chromatographic techniques including silica gel column chromatography, sephadex LH-20 and preparative HPLC. Their structures were determined by analysis of spectral data as tenuistone L (1), tenuistone K (2), sakuranetin (3), pachypodol (4), retusin (5), penduletin (6), casticine (7), 3, 7-dimetoxi-5, 3′, 4′-tri-hidroxiflavona (8), eupatin (9), (+)-miliusol (10), miliusane XIX (11), miliusane XVIII (12), miliusolide (13), 19, 20-dihydromiliusolide (14), debilisone C (15), goniothalamusin (16), 2, 10-dihydroxy-3, 9-dimethoxy-8-oxo-protoberberine (17), consanguine B (18), 6β-hydroxystigmasta-4, 22-dien-3-one (19) and 6β-hydroxystigmast-4-en-3-one (20), respectively. Among them, compounds 1 and 2 are new compounds, compounds 6, 9, 18 and 20 are isolated from Annonaceae plants for the first time and compounds 5, 7, 17 and 19 are isolated from the genus Miliusa for the first time. Human triple negative breast cancer cells (MDA-MB-231 and BT-549) were used to evaluate the antitumor activity of these isolates by MTT assay. Compounds 10 and 11 showed significant anti-proliferation activity against the test cells with half inhibition concentration (IC₅₀) of 0.98-4.85 μmol·L^-1.