Abstract: The evaluation of uncertainty in the determination of chloramphenicol in shellfish aquatic products by liquid chromatography mass spectrometry was established based on the mathematical model.Valuate and analyze the influence of uncertainty components from different sources on the measurement results. The calculation results are quantified according to the standard uncertainty of each component. The relative standard uncertainty is 0.053 and the expanded uncertainty was 1.43 μg/kg. The results showed that the chloramphenicol content in the sample should be expressed as(13.5±1.5) μg/kg(with 95% confidence probability,contains factor K=2). According to the calculation results of the ratio determination of each component,the concentration of chloramphenicol in the sample solution,the volume added by internal standard and the volume fixed by sample treatment solution V have a great influence on the uncertainty of the determination method,which could provide a theoretical basis for improving the quality control system of chloramphenicol content in shellfish aquatic products by this method.