Abstract: The chemical constituents of solid rice culture of the endophytic fungus Aspergillus sp.Dq-25 from barnacle were isolated and purified by silica gel, Sephadex LH-20, C₁₈ reversed silica gel column chromatography and recrystallization.Their structures were identified by the physical and chemical properties, and by various spectroscopic methods.Six compounds were isolated and identified as: demethyldihydropenicillic acid (1), dihydropenicillic acid (2), penicillic acid (3), fortisterol (4), 22E, 24R-3P, 5a-dihydroxyerogosta-7, 22-diene-6-one (5), and (22E, 24R)-ergosterol-7, 22-diene-3β, 5α, 9α-triol-6-one (6).Compound 1 was a new butyrolactone.MTT method was used to analyze cytotoxicity, and the result showed that compound 3 exhibited inhibitory activity on five cell lines, including K562, HeLa, SGC-7901, A542 and BEL-7402, with IC₅₀ values of 38.0 ~ 105.0 μmol/L.