Abstract: To establish an analytical method for the determination of niclosamide in aquatic products by QuEChERS / liquid chromatography-tandem mass spectrometry,the sample was extracted with acetonitril,the extract was cleaned up with C_18 and Alumina-N,the mass spectrometer was operated in the negative ion mode using selected reaction monitoring for the qualitative and quantitative analysis. The linear ranges were from 0.5 to100 ng / m L with a good linear relationship( R~2= 0.9996).The detection limits of this method for niclosamide residues were 0.2 μg / kg,and the limits of quantification were 0.4 μg / kg.The relative standard deviations ranging from 4.33%~9.91%( n = 5) and the average recovery rates were from74.6% ~ 92.1%. The method proposed by this paper possessed higher applicability and selectivity. It is promising in real applications of determining the niclosamide residues in aquatic products.