Abstract: A sensitive liquid chromatography tandem mass spectrometry method with isotopic label d5-chlormphenicol as internal standard was developed to determine trace amounts of chloramphenicol residue in pork. The pork powder were extract for 4 times by adding 10 mL 0.1 mol sodium acetate buffer solution (pH＝5) and 20 mL ethyl acetate. Oasis solid-phase extraction and liquid-liquid partitioning were used to clean the aqueous solutions. The limits of detection (LOD) is 0.004 ng·g^－1, and the limits of quantification (LOQ) is 0.02 ng·g^－1．The linear range is between 0.01 ng·g^－1 and 0.5 ng·g^－1．The average recoveries are in the range of 99％—109％ with the relative standard deviation less than 1.5％.