Hypoxylonone, a new oxa-bridged seven-membered ring analog from fungus Hypoxylon cf. subgilvum SWUF15-004A new oxa-bridged seven-membered ring analog, hypoxylonone (1), and thirteen known compounds (2-14) were isolated from fungus Hypoxylon cf. subgilvum SWUF15-004.The structures were elucidated by the analysis of spectroscopic (IR, 1D and 2D NMR), HRESIMS and X-ray diffraction (MoKα) data. Several isolated compounds were evaluated for cytotoxicity against four human cancer cell lines (HeLa, HT29, MCF-7, A549). Compound 1 exhibited weak inhibitory effects of the nitric oxide production in RAW264.7 cells. Compounds 8 and 9 exhibited slight cytotoxicity.