Abstract: 5% ethofenprox spreading oil (SO) was developed by orthogonal experiment through the screening of the solvent and surfactant. The optimum solvent was 50.0% methyl laurate. The proportion of the mixture of surfactant, OP-4, OP-10, 2201 and dodecanol ester, was 4∶ 4∶ 3∶ 9 (m/m), which was 10.0% weight in total of the formulation. The other component was soybean oil, which was 35.0% of the formulation. The formulation had been stored at (54 ℃±2 ℃) for 14-days without precipitation, crystallization and layer-separation. The decomposition rate was 0.10%. Surface tension was 28.33 mN/m and interfacial tension was 0.11 mN/m at 35 ℃. Spreading speed and area reached 9.29 cm/s and 1 882.74 cm2 with 1.28 μ L.This formulation could be directly dropped to paddy water without any dilution. The active ingredient dropped on paddy water surface and spreaded to whole water surface of the paddy field in a few minutes. The field application showed that after 7 d the corrected control efficacy of 5% ethofenprox SO against rice planthoppers was 78.52%.