A gas chromatography–tandem ion trap mass spectrometric（GC-MS/MS） method was developed for the simultaneous determination of four barbiturates residues（e.g.barbital,amobarbital,secobarbital sodium and phenobarbital） in pig liver and kindey.The barbiturates residues were extracted by ultrasonic assistant extraction with acetonitrile.The extracts were concentrated and redissolved by 5 mL 0.1 mol/L K2HPO4 （pH 7.4）,cleaned up by C18 SPE cartridge using hexane–ethyl acetate（7∶3） mixture as eluting solvent,then derivatized with CH3 I by microwave irradiation.The methylated barbiturates were separated on a TR-5MS capillary column and detected with an ion trap mass detector.Electron impact（EI） ion source operated in MS/MS mode was adopted for identification and external standard method was employed for quantification.Good linearities （r＞0.99） were obtained in the range of 5-100 μg/L.The limits of detection（LOD,S/N≥3）for four barbiturates were no more than 0.65 μg/kg in liver and 1.00 μg/kg in kidney.The limits of quantitation（LOQ,S/N≥10） were no more than 2.20 μg/kg in liver and 3.35 μg/kg in kidney.The recoveries of four barbiturates at spiked levels of 5，10，15 μg/kg ranged from 68% to 90% with relative standard deviations（RSDs） no more than 10%.The results indicated that the method was accurate for the determination of barbiturate drug residues in animal tissues.