A method was established for the determination of carbofuran，aldicarb and its metabolite in groundwater by liquid chromatography-electrospray ionization tandem mass spectrometry with direct injection.The optimization conditions of LC and MS were discussed.Methanol and water were chosen as mobile phase.Under the optimal conditions,the calibration curves for carbamate and its metabolite were linear in the range of 0.05-100 μg/L, with correlation coefficients between 0.996 0 and 0.999 3.The limits of detection(S/N≥5) were between 0.01 μg/L and 0.05 μg/L.The recoveries of target compounds at three spiked concentration levels ranged from 90% to 106% with relative standard deviations(RSDs, n=8)of 2.7%-6.5%.This method was accurate and sensitive, and was suitable for the trace determination of carbamate in groundwater.