The present invention relates to a compound of Antrodia camphorata used for liver protection, in particular to an extract, 4-hydroxy-2,3-dimethoxy-6-methyl-5(3,7,11-trimethyl-dodeca-2,6,10-trienyl- )-cyclohex-2-enone which is isolated from Antrodia camphorate. The cyclohexenone compound according to the invention helps to alleviate liver injury and fibrosis induced by chemicals and reduces the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). By increasing the contents of glutathione peroxidase (GSHPX) and catalase (CAT), cyclohexenone further decreases the liver damage and the oxidative pressure caused by free radicals, enhances the antioxidant ability and achieves the purposed of liver protection.