A simple,sensitive and reliable analytical method was developed for the simultaneous determination of 16 cephalosporins in formulated feeds by ultra high performance liquid chromatography-positive electrospray ionization tandem mass spectrometry.Samples were extracted with acetonitrile-water(40∶60) solution,and directly diluted using 0.1% formic acid solution after centrifugation,then analyzed by LC-MS/MS.The samples were separated on an Acquity UPLC BEH C18 column with a mixture of 0.1% formic acid solution and methanol as mobile phase by gradient elution,and detected in multiple reaction monitoring mode.The matrix matched external standard method was applied for the quantitative analysis.There are good linear relationships for sixteen cephalosporins in the certain concentration ranges with their correlation coefficients more than 0.999.The limits of detection for sixteen cephalosporins were in the range of 1.5-15 μg/kg,and the limits of quantitation were 5.0-50 μg/kg.The recoveries for the analytes in feeds at spiked levels of 10-2 500 μg/kg were in the range of 88.4%-93.6%,with relative standard deviations of 0.8%-4.7%.The method is suitable for the determination of sixteen cephalosporins in formulated feeds due to its simplicity and reliability.