A high performance liquid chromatography-tandem mass spectrometric(HPLC-MS/MS) method was developed for the determination of five nitromidazoles in aquatic products.Samples were extracted with acetonitrile containing 0.1%(by volume) ammonium hydroxide,and then purified with a mixture of anhydrous sodium sulfate,C18-N and NH2-PSA.The analysis was performed by an HPLC-MS/MS system with Merck Chromolith Performance RP-18e(4.6 mm×100 mm) column.The mobile phase consisted of methanol and 0.1%(by volume) formic acid solution by gradient elution,and multiple reaction monitoring(MRM) mode with positive electrospray ionization was used.The effects of the dosages of ammonium hydroxide in extractant and anhydrous sodium sulfate,C18-N and NH2-PSA in cleaning-up agent were studied.Under the optimized analytical conditions,the calibration curves for five nitromidazoles were linear in the concentration range of 20-500 μg/L with their correlation coefficients(r2) not less than 0.998 9.The recoveries at three concentrations ranged from 77.2%to 94.8%with the LOQs of 0.7-2.0 μg/kg.The method is suitable for the determination of 5 nitromidazoles in aquatic products.