Abstract: To screen novel botanical fungicides, the investigation on the chemical constituents of the aerial parts of Cirsium japonicum was carried out. The plant was extracted with methanol. After liquid-liquid extraction, separation by silica gel and Sephadex LH-20 column chromatography, 13 compounds were finally obtained from the ethyl acetate phase. By comparing the NMR and MS data of the compounds with the data in literatures, they were identified as ciryneol D ( 1 ), 12β, 20(S)-dihydroxydammar-24-en-3-one ( 2 ), 9(11), 12-dieneoleana-3β-ol ( 3 ), taraxasterol ( 4 ), 3β-hydroxystigmast-5-en-7-one ( 5 ), 3β-hydroxyl-12(13)-en-olean-11-one ( 6 ), p-coumaric acid ( 7 ), obtucarbamate A ( 8 ), methyl 4-hydroxybenzoate ( 9 ), 4,4′-diphenylmethane-bis(methyl) carbamate ( 10 ), quercitrin ( 11 ), kaempferol-3-O-α-L-rhamnoside ( 12 ) and chrysoeriol-7-O-2′-O-6′-O-acetyl-β-D-glucopyranosyl-β-D-glucopyranoside ( 13 ). Among them, 2 , 3 , 6 , 8 , 10 , 12 and 13 were isolated from this plant for the first time. Ciryneol D ( 1 ) showed inhibitory effect against the mycelia growth of five species of plant pathogenic fungi. Among all the tested microorganisms, compound 1 showed best effect against Valsa mali with the EC₅₀ value of 23.2 μg/mL. It also exhibited significant inhibition on the spore germination of Curvularia lunata, Colletotrichum gloesporioides and Botrytis cinerea, with the EC₅₀ values of 27.5, 26.4 and 81.9 μg/mL, respectively.