In　order　to　rapidly　determine　the　organophosphorus　pesticide　residue　in　vegetables,　esterases　are　extracted　from　four　types　of　wheat,　i.e.　Jing　No.9428,　Jing　No.9583,　Jingdong　No.8　and　Jing　No.2.　The　inhibition　rates　of　the　esterase　activity　under　different　concentrations　of　parathion　are　compared　by　the　colorimetric　measurement.　The　results　indicate　that　the　inhibiting　sensitivities　to　parathion　of　esterase　extracted　from　different　wheat　are　not　the　same.　The　esterase　from　the　wheat　of　Jing　No.2　is　more　sensitive　to　parathion　than　that　from　others,　with　detection　limit　of　3.0　×　10-7　mg/L.　Simultaneously,　the　temperature,　time　and　pH　of　the　enzymic　reactions　are　optimized.　Organophosphorus　pesticide　residues　in　vegetables　are　determined　by　the　proposed　method.