Abstract: A GC-MS method for the investigation on the metabolism of 6-methoxy n-butylphthalide(MBP)is described.After oral administration of MBP,the rat urine sample was collected,hydrolyzed with β-glucuronidase,extracted and concentrated for TMS derivatization,and thenanalyzed by GC-MS.MBP and its six oxidative metabolites were determined in the 0～24 h rat urinesample. The mass spectra of the metabolites and their derivatives were presented and the in vivometabolic pathway was discussed.