Residues of prometryn in edible tissues of codfish, grass carp, channel calfish, catfish, laver were determined by gas chromatography-tandem mass spectrometry (GC-MS/MS) using internal standard method. Such factors as extraction solvent, solvent dosage and choice of solid-phase extraction (SPE) columns were compared in this paper. The target compound was extracted two times with acetonitrile,purified by solid-phase extraction (SPE) with Envi-Carb column and LC-NH₂ column. and analyzed with GC-MS/MS. TR-5MS capillary chromatographic column was used for separation, and the selected reaction monitoring(SRM) with electron impact ionization source was adopted in MS. This method chooses d14-prometryn as internal standard substance. The working curve were linear (r²=0.999) in the range of 5-100μg/L. When spiked with 5.0, 10.0, 25.0μg/kg of prometryn and 10.0μg/kg d14-prometryn, the average recoveries were 82.0%-111.2% and the RSD were 1.2%-6.0%. The detection limit was 0.5μg/kg. The method could meet the requirements of the residul detection. It is suitable for qualitative and quantitative determination of samples.