Abstract: Eight polyacetylenes were isolated from the extract of the stems and leaves of Chrysanthemum morifolium by various chromatographic methods. Their structures were determined as 2E,4E,12Z-tetradecatriene-1-pyrrolidine-1-oxo-8,10-diynoic (1), tetradeca-2E,4E,12E-trien-8,10-diynoic acid pyrrolidide (2), tetradeca-2E,4E-dien-8,10-diynoic acid pyrrolidide (3), tetradeca-2E,4E,10Z-trien-8-ynoic acid pyrrolidide (4), 2E,4E,12E-tetradecatriene-8,10-diynoic acid isobutylamide (5), 2E,4E-undecyldiene-8,10-diynoic acid isobutylamide (6), 2E,4E,10E-N-isobutyl-2,4,10-tetradecatrien-8-ynoic acid amide (7), and undeca-2E,4E-diene-8,10-diynoic acid phenylethylamide (8) by spectroscopic methods, including UV, IR, ESI-MS, HR-ESI-MS, 1D and 2D NMR spectra. Among them, compound 1 is a new polyacetylene, and compounds 2-8 were isolated from this plant for the first time. Compounds 5-8 inhibited the proliferation of A549 cell significantly at certain concentration, showing potent antitumor activity.