Abstract: Sulfonam ides are widely used in fisheries for prevention of d iseases.W ith the public. sincreasing concern withthe food safety, residues of sulfonam ides infishery products should arouse regards.Improper use or miproper withdraw tmiewill lead to the presence of sulfonam ide residues in fishery products, which can influence human food security and polluteenvironment possibly.M any countries have established the maxmium allowable residue lmiits for sulfonam ides in fisheryproducts1T herefore, it is necessary to establish the analys is method for the detection of sulfonamides residues in fisheryproducts.A method of smi ultaneous determ ination of twenty-one commonly used sulfonam ideresidues inTrionyx sinensis by high performance liquid chromatography-electro spray tandem mass spectrometry (HPLC /MS /MS) is described.Sulfonamide residues were extracted from hom ogenized tissue with aceton itrile and dichlorom ethane.A part of theextract was taken and then dried by n itrogen.The residue were dissolved into 1mL mobile phase and defatted w ith n-hexane( saturated by acetonitrile) 1T he 21 analytes w ere separated on ZORBAX EclipseXDB-C8 Column w ith mobile phasescontainingm ethanol and 012% acet ic acid and finally determ ined by electrospray ion ization tandem m ass spectrometry( ESI-MS-MS).A linear gradient eluting programo fmethanol from 30% to 80%(V /V)was employed at a flow rate of 012mL /m in in 35m inutes1Ana lytes confirmation were perform ed usingm ultiple reaction monitoring (MRM) with one precursorionand two productions as identifiers1T he quantitative lmi it of method was 4Lg /kg1Recoveries tested by standardaddition method were in the range of 7512% )104%, RSDs were in the range of0116% ) 9198% at a spiking level from4Lg /kg to 40Lg /kg(n= 6).