Abstract: Objective A liquid chromatography-tandem mass spectrometry(LC-MS/MS)method was developed to quantify and confirm the presence of dimetridazole(DMZ)and its hydrox ylated metabolite DMZOH in eggs.Methods Deuteriated DMZ was employed as an internal standard.Samples were extracted with ethyl acetate,then evaporate just to dryness under nitrogen.The residue was redisso lved in 0.1% formic acid-hexane(1+1,v/v),formic acid phase was used for analysis.Quantitative results were based on multiple reaction monitoring mode after ionization in the positive electrospray ionization mode.Results The calibration curve of DMZ and DMZOH showed good linearity in the range of 0.03~50 μg/L with correlation coefficient of 0.998 9 and the range of 0.11~50μg/L with r=0.999 6 respectively.The detection limits were 0.009 μg/kg and 0.03 μg/kg.The average recoveries at three spiked levels(1,4,10 μg/kg)were between 90.4% and 98.5% within CV<4.4% for DMZ,and between 85.2% and 102.5% within CV<5.6% for DMZOH.Conclusion The method can identify and quantify DMZ and its metabolite DMZOH in eggs.It is simple and sensit ive,suitable for statutory residue testing.