Cirsium is a genus of perennial and biennial flowering plants in the Asteraceae, one of several genera known commonly as thistles. They are mostly native to Eurasia and northern Africa, with about 60 species from North America. Sixty-seven components were identified in the essential oil from the rhizomes of Cirsium japonicum DC., with palmitic acid (14.42%), caryophyllene oxide (12.57%), khusinol (6.31%), pentadecanoic acid (6.28%) and myristic acid (4.66%) as the major components. Terpenoids accounted for about 45.22%, especially sesquiterpenoids, which comprised 42.17% of the essential oil. Twelve compounds were isolated from the rhizomes of Cirsium japonicum DC., and their structures were cis-8, 9-epoxy-heptadeca-1-ene-11, 13-diyne-10-ol, ciryneol A, 8,9,10-triacetoxyheptadeca-1-ene-11,13-diyne, ciryneone F, cireneol G, ciryneol H, ciryneol C, p-coumaric acid, syringin, linarin, beta-sitosterol and daucosterol.