Abstract: Four cadinane-type sesquiterpenes were obtained from the petroleum ether of 95% ethanol extract of Eupatorium adenophorum Spreng by using an HP-20 macroporous resin column, silica gel, and semi-preparative HPLC. Their structures were determined by physical, chemical and spectroscopic methods and identified as eupatorinol (1), (+)-(5R,7S,9R,10S)-2-oxocadinan-3,6(11)-dien-12,7-olide (2), (1S,4R)-7-hydroxycalamenen-3-one(3) and (-)-(5R,6R,7S,9R,10S)-cadinan-3-ene-6,7-diol (4). Among them, compound 1 is a new cadinane-type sesquiterpene, and compound 3 was isolated from this genus for the first time. In bioassay, none of these compounds displayed obvious cytotoxicity.