A new and sensitive analytical method was developed for the simultaneous determination of eighteen carbamate pesticides in biological samples by on-line solid phase extraction(on-line SPE) coupled with liquid chromatography-linear ion trap mass spectrometry(LC-LIT/MS).The samples were treated with acetonitrile,followed by dilution and centrifugation.The resulting solution was injected into LC system directly and processed with an Waters Oasis? HLB On-line SPE column for enrichment and purification.Separation was performed on a BETASIL C18 column with mixed mobile phases of methanol and water(both containing 0.1% formic acid) by gradient elution.The analytes were detected in selected reaction monitoring(SRM) or consecutive reaction monitoring(CRM) mode through positive electrospray ionization(ESI+).The calibration curves were linear within the investigated mass concentration ranges of the analytes(weighted 1/X),with correlation coefficients(r2) of 0.9943-0.9994.The LODs were in the ranges of 0.1-5ng/mL for whole blood and urine,and 0.1-5ng/g for liver tissue.The recoveries at three spiked levels ranged from 90.2% to 114.5%,with RSDs(n=4) of 0.5%-7.5%.The developed method is simple and accurate,and is sensitive for the rapid determination of eighteen carbamate pesticides in biological samples.