In the pH 7.2 Na₂HPO₄-NaH₂PO₄ buffer solutions and in the presence of PEG-6000,fenvalerate (Fen) antisera was combined with Fen specifically,and aggregated to form immune complex particles that exhibited five resonance scattering peaks at 350,390,420,440 and 480 nm respectively.The peak at 390 nm was the strongest and was chosen for use.Fen concentration (c) in the range of 0.20 to 6.40 μg·mL^-1 was proportional to the resonance scattering intensity at 390 nm.Its regression equation was ΔI_RS =23.05c-1.39,the correlation coefficient was 0.997 8,and the detection limit was 0.07 μg·mL^-1 .Effects of buffer solution type,pH value,buffer solution volume,fenvalerate antisera concentration,PEG-6000 concentration,incubation temperature and time on the resonance scattering intensity were considered in detail.With pH(5.8-8.0)increasing,the IRS and Ib all decreased.When the pH value was at 7.2,the ΔI_RS was bigger.Three buffer solutions of pH 7.2,including Na₂HPO₄-citric acid,Na₂HPO₄-KH 2PO 4 and Na₂HPO₄-NaH₂PO₄,were examined.The pH 7.2 Na₂HPO₄-NaH₂PO₄ buffer solution gives the biggest ΔI_RS value.PEG-6000 could enhance the ΔI_RS value.When the concentration of PEG-6000 was 50.0 mg·mL^-1,the ΔI_RS was achieved at max.Fen was a stable chemical.The IRS increased withiN₂0 min,while the ΔI_RS remained constant when incubation time was in the range of 20-40 min.The condition of a pH 7.2 Na₂HPO₄-NaH₂PO₄ buffer solution-50.0 mg·mL^-1 PEG-6000-6.67 μg·mL^-1 Fen antisera-30 ℃-incubation time 20 min was chosen.According to the procedure,the influence of foreign substances on the determination of 1.60 μg·mL^-1 Fen was examined,within a relative error of ±5％. Results showed that the following coexistent substances had no impact on the RS assay:96 μg·mL^-1 ametryne,96 μg·mL^-1 m-aminotoluene,48 μg·mL^-1 simetryne,48 μg·mL^-1 p-aminotoluene,80 μg·mL^-1 BSA,80 μg·mL^-1 HSA,80 μg·mL^-1 Fe3＋,80 μg·mL^-1 Mg2+,160 μg·mL^-1 Ca2+,and 160 μg·mL^-1 glucose.The results indicated that this RSS assay has good selectivity.This immune resonance scattering spectral assay was applied to the determination of Fen in waste water samples with satisfactory results.The recovery was in the range of 92.91%-101.25%,and the relative standard deviation was in the range of 1.71%-4.80%.