Abstract: OBJECTIVE To investigate the degradation products of febuxostat. METHODS After forced degradation, products were determined by LC-MS. The structures of degradation products were elucidated by the results of mass spectrometry combined with the structure and the reaction mechanism. RESULTS It was speculated that the degradation products were 2-(3-cyano-4-isobutoxy-phenyl)-4-methyl-thiazole-5-carboxylic acid methyl ester, 2-(3-carbamoyl-4-isobutoxyphenyl)-4- methylthiazole-5-carboxylic acid, 2-(3-cyano-4-isobutoxy-phenyl)-4-methyl-1-oxidation thiazole -5-carboxylic acid methyl ester, a dimmer of febuxostat. CONCLUSION The method provides a reference of studying the stability of febuxostat and possible degradation pathway.