Abstract: An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed for the quantitative detection of deltamethrin.The haptens of deltamethrin 1-carboxy-(3'-phenoxyphenyl)methyl-3-(2',2'-dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate (Med) and N-2-(carboxy-propyl)carbamoyl-(3'-phenoxyphenyl)methyl-3-(2',2'-dibromoethenyl)-2,2-dimethylcyclopropane-carboxylate (Di) were synthesized.Di was conjugated with bovine serum albumin (BSA) as immunogen (Di-BSA) by carbodiimide method and coating antigens (Di-OVA,Med-OVA) of deltamethrin were prepared by conjugating these two haptens with ovalbumin (OVA) by mixed anhydride method.Polyclonal antibodies were obtained from rabbits immunized with immunogen and the titer of the freeze-dried powder (2.5×105) was determined by indirect non-competitive ELISA procedure.Standard competitive curve of the optimized ic-ELISA for deltamethrin was developed.Thus,the optimized assay conditions such as concentration of methanol (30%),inonic strength (NaCl 0.4 mol/L),pH value (7.5) were investigated and obtained by analysis of heterologous.The value of 50% inhibition of antibody binding (IC50) for deltamethrin was 0.55±0.05 mg/L,and the low detection limit (IC10) was 3.76±0.35 μg/L.This ELISA assay had no cross-reactions significantly with other major pyrethroids.Tap water,river water and soil samples were spiked with deltamethrin at 0.05~5.0 mg/L(or mg/kg),the average recoveries were in the range of 89.7% ~106.8%,82.4% ~101.7%,75.6% ~97.8% respectively.