Abstract: A G-C-MS method for the analysis of tramadol and its four metabolites in human urine is described. The urine samples were acid hydrolyzed with hydrochloric acid, cleaned with diethyl ether and extracted with dichloromethane—isopropanol (9:1). After derivatization, the solution was analyzed with GC-MSD. Tramadol and its 4 metabolites were detected in urine samples 2～40 hours after oral administration. The recovery of tramadol was 85.2%±5.4(n=3), the detection limit was down to 12.5 pg. The derivatization methods was discussed.