A method was developed for the determination of amitraz,chlordimeform and their metabolites in blood by gas chromatography-tandem mass spectrometry(GC-MS/MS).The conditions for sample pretreatment and GC-MS/MS parameters were optimized.The samples were pretreated by solid supported liquid extraction(SLE),and eluted with acetonitrile-dichloromethane(1∶1).The detection was carried out by GC-MS/MS in multiple reaction monitoring(MRM) mode.Good linear relationships for 2,4-dimethylaniline(DMA),4-chloro-2-methylaniline and amitraz were obtained in the range of 1.0-1 000 ng/mL,and those for other three compounds were obtained in the range of 2.0-1 000 ng/mL,with correlation coefficients more than 0.99.The limits of quantitation were in the range of 1.0-2.0 ng/mL,and the recoveries ranged from 88.6% to 113%.With the advantages of simplicity,rapidness,low sample consumption,accuracy and reliability,this methed is suitable for the determination of six compounds in blood.