Abstract: A reasonable, reproducible and operational gas chromatographic-mass spectrometry (GC/MS) for detecting clenbuterol was developed through reviewing and evaluating many various determination methods of clenbuterol. The composite sample was extracted with 0.1 mol/L perchlorate solution, centrifuged, neutralized, followed by extracting with isopropanol-ethyl acetate (1∶9, v/v). After evaporation of organic solvent, the residues was dissolved with potassium dihydrogen phosphate buffer solution, and applied to a SCX cartridge successively. The drug was eluted from the cartridge with 3% ammonia water methanol solution, and the eluate was evaporated to absolute dryness. After toluene and B-STFA were added to the residues, the drug was derivatived at 80 ℃ for 1 h, then cooling, more toluene was added and applied to GC/MS. SIM mode was performed at m/z 86, 243, 262 and 277. The range of linearity was 5.00-1 000 μg/L, and relevant coefficient was more than 0.999, and the method detection limits were about 1 μg/kg or 1 μg/L. Recoveries from pig’s liver and urine fortified at 1, 10 and 100 μg/kg or 1 μg/L were 73.4%- 96.8%and 84.4%-92.2% respectively, RSDs were 7.0%-16% and 6.0%-11% respectively, and from swine muscle and feed at 10 μg/kg were 81.5% and 70.6%, respectively. RSDs were 5.8% and 4.5%, respectively.