A novel method was developed for the determination of thirteen nitroimidazoles in fish blood by ultra performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS） with supramolecular solvent based dispersive liquid-liquid microextraction.The target compounds in fish blood were extracted with a supramolecular solvent consisted of octanol,tetrahydrofuran and water.The analytes were separated on a Waters ACQUITY UPLC BEH C18 column（2.1 mm×50 mm×1.7 μm） by gradient elution with acetonitrile-water as mobile phases.The qualitative and quantitative analyses were conducted by electrospray ionization mass spectrometry in positive ion mode under multiple reaction monitoring（MRM） mode.Experimental results demonstrated that good linearities for the analytes were observed in their respective concentration ranges with correlation coefficients（r2） larger than 0.998.The limits of detection（LOD） and the limits of quantitation（LOQ） were in the ranges of 0.05-0.2 μg/L and 0.1-0.5 μg/L,respectively.Recoveries for 13 nitroimidazoles at three spiked levels ranged from 88.4% to 105% with relative standard deviations（n=6） of 4.3%-11%.The method was simple,rapid,accurate and reliable,and could be used for the analysis of nitroimidazole residues in fish blood samples.