Pirimicarb (2-(dimethylamino)-5,6-dimethylpyrimidin-4-yl-N-dimethylcarbamate) is one of the class of substituted N-dimethylcarbamate insecticides.A primary pathway for the transformation of pirimicarb in aquatic environments is hydrolysis.In this paper, we focus on hydrolysis of pirimicarb affected by pH and temperature.The Agilent 1100 series LC system was coupled on-line to LC/MSD Trap XCT ion-trap mass spectrometer (Agilent Technologies, CA, USA).with a Zorbax C 18 column (250mm × 4.6mm i.d.,5μm).The solvents used as mobile phase were methanol and water.The products of hydrolysis were analyzed by LC-ESI-MS.Fig.1 shows the mass spectra of the hydrolysis product 2-dimethylamino-5,6-dimethylpyrimidin-pyrimidine.