A method for the determination of three antibiotic drugs,including chloramphenicol(CAP),thiamphenicol(TAP) and florfenicol(FF) in feed was developed using high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).The target analytes were extracted with basic ethylacetate,and evaporated to dryness.The extracts were defatted with hexane and cleaned up by liquid-liquid partition.Three analytes were detected with electrospray ionization(ESI) in negative mode using multiple reaction monitoring,and quantified by the internal standard method.Under the optimal conditions,the calibration curves of chloramphenicol,florfenicol and thiamphenicol were linear in the ranges of 0.2-10.0,0.2-10.0 μg/L and 1.0-50.0 μg/L,respectively,with correlation coefficients not less than 0.990 0.The limits of detection(LODs) were 0.1，0.1,0.5 μg/kg, and the limits of quantitation(LOQs) were 0.3,0.3,1.5 μg/kg,respectively.The average recoveries ranged from 77% to 108% with RSDs not more than 10.9%.