A rapid method of liquid chromatography tandem mass spectrometric（HPLC-ESI MS/MS） with isotope dilution was developed for the simultaneous determination of residual mebendazole（MBZ） and its metabolites e.g. hydroxy mebendazole（MBZ-OH） and amino menbendazole（MBZ-NH2） in fishery products.The sample,after adding disodium phosphate,was extracted with ethyl acetate.The extract was evaporated to dryness under nitrogen,and redissolved in 2 mL methanol-0.1% formic acid（1∶1,by volume）.The solution was defatted with n hexane.The targeted compouds were seperated on Hypersil GOLD C18 column（100 mm×2.1 mm i.d.,3 μm） using methanol-0.1% formic acid as mobile phase at a flow rate of 0.2 mL/min,and analyzed by a triple quadrupole tandem mass spectrometer with a heated electrospray ionization source（HESI） and selected reaction monitoring（SRM）.The standard curves were linear in the range of 0.5-100 μg/L for three analyzed drugs with correlation coefficient（r2） not less than 0.999 2.At spiked levels of 1-40 μg/kg in grass carp,crayfish and soft shelled turtle blank muscle sample,the average recoveries of MBZ,MBZ-OH and MBZ-NH2 ranged from 91% to 112% with their relative standard deviations（RSDs） of 1.5%-10.7%.The detection limits for all the target compounds were 0.5 μg/kg and the quantitation limits were 1.0 μg/kg.The results showed that the method was simple,sensitive and accu rate,and was suitable for the simultaneous qualitative and quantitative confirmations of menbendazole and its metabolites residues in fishery products.