To identify the drug-metabolizing enzymes involved in the hydroxylation of the new anti-inflammatory and anodyne imrecoxib.Imrecoxib was incubated with heterologous expression human cytochrome P450 (rCYPs) in vitro, and metabolites and remained parent drug were detected with liquid chromatography-multistage mass spectrometry. The contribution of 4 CYPs in the hydroxylation metabolism of imrecoxib was evaluated by total normalized rate (TNR) method.Imrecoxib is metabolized by CYP2C9, CYP2D6 and CYP3A4, with the rate of 62.5%, 21.1% and 16.4%, respectively.CYP2C9 is the major enzyme involved in imrecoxib hydroxylation metabolism.