Abstract: A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the quantitative determination of mebendazole in aquaculture water.The limit of quantification was 0.5 μg/L.The average recoveries of the three spiked levels ranged from 79.0% to 93.9%.The intra-day and inter-day relative standard deviations (RSDs) were 7.57%-8.27% and 7.43%-8.11%,respectively.The actual application concentrations of 15 μg/L and 50 μg/L were used as the tested concentrations for the elimination experiments of mebendazole in aquaculture water,respectively.The results showed that mebendazole was a photosensitive drug whose photodegradation followed the first-order kinetics.The photolytic degradation rate of mebendazole in outdoor aquaculture water under natural light was more than 80% after 648 h.The elimination half-life of mebendazole was 231.05 h at 15-18℃.At the end of the experiment (648 h),6.4 μg/L of mebendazole was still detected in the high concentration group(50 μg/L).Therefore,the results of this study could provide basic data for the pharmacokinetic study of mebendazole in aquaculture animals.