Abstract: In order to study the safety of ethiprole to paddy soil ecosystem,residue decline of ethiprole in soil and water were investigated under field and field-simulated condition.The samples were extracted by acetic-acetonitrile(1∶99, V∶V),cleaned up with primary secondary amine (PSA),and analyzed by UPLC-MS/MS.External reference method was used for quantitative determination.The linearity was satisfied (r>0.98) in the concentration range of 0.001-0.1 mg/L.The limit of detection(LOD) was 2.2×10-13 g,and the limit of quantification (LOQ) in paddy soil and water were 0.001 mg/kg(L).The average fortification recoveries varied from 80.2% to 119.5% with relative standard deviation (RSD) of 3.1%-9.0% when ethiprole was spiked at 0.002-1.0 mg/kg level in soil matrix,the average fortification recoveries varied from 94.2%-108.2% with relative standard deviation (RSD) of 1.6%-13.2% when ethiprole was spiked at 0.001-1.0 mg/L level in water matrix.The decline study of ethiprole residue in paddy field soil and water were carried out,the decline curves accorded with the first-order kinetics equation,and the half-lives of ethiprole in soil and water under field-simulated and field condition were of 3.2-2.8 d and 3.5-1.8 d,respectively.Ethiprole belongs to the easily degradable pesticide.