A method for the simultaneous determination of residue of pretilachlor and simetryn in rice filed environment by ultra-performance liquid chromatography tandem mass-spectrometry( UPLC-MS/MS) was established.The residues in unpolished rice,rice husk,plant,soil and field water were extracted by acetonitrile,purified by N-propyl ethylenediamine.The residues of pretilachlor and simetryn in samples were determined by UPLC-MS/MS.Pretilachlor showed a good linear relationship in the range of 0.01 ~ 5.0 mg/L with t...