Abstract: When enrofloxacin residue is close to the maximum residue limit in aquatic products,it is very important to carry out evaluation of measurement uncertainty to accurately determine whether the products meet the quality standards.So a method of uncertainty evaluation for the determination of enrofloxacin residue in aquatic products by liquid chromatography was established.According to "Evaluation and Expression of Uncertainty in Measurement"(JJF 1059.1-2012)and "Guidance on Evaluating the Uncertainty in Chemical Analysis"(CNAS-GL06:2006),a mathematical model was constructed and the uncertainty sources were analyzed,and then the main components of uncertainty were quantified and combined.Finally the expanded uncertainty was achieved.When the measured value of enrofloxacin residue in aquatic products was 97.1 μg/kg,its expanded uncertainty was 5.6 μg/kg.The results showed that the major factors of uncertainty were sample pre-treatment and standard solution.The uncertainties of sample pre-treatment and standard solution accounted for more than 50% and 22% of the total uncertainties,respectively.