Abstract: HPLC was applied to the determination of residual sulfanilamides and ethylaminopyrimidines in aquatic products.The residual drugs in the sample were extracted with a solvent mixture of acetonitrile,dichloromethan and ethyl acetate mixed in the proportion of 2∶1∶1 respectively.The extract obtained was defatted and purified by extraction with hexane,and the hexane extract was then concentrated by evaporation.The residue was taken up with a mixed solvent of acetonitrile,acetic acid(2+98) and H2O mixed in the ratio of 15+25+60,which was used also as the mobile phase in the chromatographic separation later.Seven kinds of sulfanilamide and ethylaminopyrimidine drugs were well separated by gradient elution on the chromatographic column of Clovisl-C18(4.6 mm×150 mm,5 μm),and their contents determined by UV-detection at the wavelength of 275 nm.Linear relationship between the peak area and the concentration of standards of the 7 different drugs were found all in range of 0.05-2.0 mg·L-1,with correlation coefficients in the range of 0.983 7 to 0.997 5.In the tests for precision,accuracy and sensitivity of the proposed method,the results obtained were as follows: RSD′s 5.85%-8.12%,recovery 62.2%-88.6%,detection limit(S/N=3) 10-50 μg·kg-1.