A sensitive and convenient method was established for the analysis of twelve kinds of pesticide in root,leaf,seed meat and seed shell of lotus,mud and field water by ultrahigh performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）.The solid samples were extracted with acetonitrile/water,then salted out with sodium chloride and following by a centrifugal separation,finally purified and eluted with a PestiCarb-SPE column.The water samples were simply enriched,cleaned up and eluted with a BondElut C18-SPE column.The eluted fractions were analyzed by UPLC-MS/MS,and quantified by the matrix external standard method.The mass fragmentation pathway and matrix effect of twelve pesticides were also investigated.The calibration curves for the target compounds were linear in the concentration range of 0005（0010）-2500 mg/L,with their correlation coefficients（r2） more than 097.The average recoveries（AR） for twelve pesticides at high,middle and low spiked levels in lotus leaf,root,seed and seed shell were between 756% and 116%,with relative standard deviations（RSDs） of 13%-251%,while the AR.for other eleven pesticides except prochloraz in mud were 646%-104% with RSDs of 09%-95%;Besides,the AR.for the analytes in field water ranged from 712% to 101% with RSDs of 09%-169%,except that the AR.for clothianidin at low level,prochloraz and indoxacarb at middle and low levels were less than 70%.The limits of quantitation（LOQs） of this method were not more than 001 mg/kg and 01 μg/L,except clothianidin.After 10% clomazone-metolachlor-prometryne granules were spread into the lotus root fields by dosages of 630 g ai/ha and 945 g ai/ha in one time,final residue test was investigated by this method.Results showed that there were no clomazone and metolachlor residues in lotus root,lotus seed and lotus leaf samples,and the residual amounts of prometryne were not more than 0022,0166,0012 and 0181 mg/kg in the lotus root,lotus seed shell,lotus seed meat and lotus leaf samples,respectively.