A method was developed for the simultaneous determination of 11 phenoxy acid herbicides in infant cereal food by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).The samples were extracted with acetonitrile containing 2% formic acid,then purified with N propyl ethylenediamine(PSA) and anhydrous magnesium sulfate(MgSO4).The target compounds were separated on a ZORBAX Eclipse XDB-C18 column(4.6 mm×50 mm,1.8 μm),and detected by HPLC-MS/MS with electrospray ionization(ESI) in negative ion mode under multiple reaction monitoring(MRM) mode,and quantified by the external standard method.The calibration curves for 11 phenoxy acid herbicides were linear in the range of 0.5-200 μg/L with their correlation coefficients(r2) larger than 0999.The average recoveries at 3 spiked levels were in the range of 77.4%-999%,with relative standard deviations(RSDs,n=7) of 1.5%-8.0%.The limits of detection(S/N=3) and quantitation(S/N=10) of the method were 0.1-2.4 μg/kg and 0.4-8.1 μg/kg,respectively.Owing to the advantages of simple operation,high accuracy and sensitivity,this method is suitable for the rapid and simultaneous detection of 11 phenoxy acid herbicides in infant cereal food.