An ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric（UPLC-ESI MS/MS） method was developed for the simultaneous determination of six benzodiazepines,including diazepam,oxazepam,nitrazepam,triazolam,estazolam and midazoalm,in animal feeds.The benzodiazepines in the feeds were extracted with alkaline tert-butyl methyl ether followed by clean-up with Oasis MCX cartridge.The LC separation was performed on a Waters Acquity UPLC BEH C18 column（50 mm×2.1 mm,1.7 μm） by gradient elution using 0.1% formic acid and acetonitrile as mobile phase at a flow rate of 0.3 mL/min.The identification of six drugs was achieved by electrospray ionization tandem mass spectrometer under multiple reaction monitoring（MRM） mode and the quantification analysis was performed by the external standard method.The calibration curves showed good linearities in the range of 5-100 μg/L.The limits of detection（LOD） for the six drugs in feeds were 2 μg/kg and the limits of quantitation（LOQ） were 5 μg/kg.The average recoveries of the six drugs at three spiked levels of 5,20,100 μg/kg were between 68% and 94% with RSDs of 5.8%-127%.The method was rapid,accurate and sensitive,and could be applicable in the routine assay on benzodiazepines in animal feeds.