Virulence of spinosad 10% suspension concentrate（SC） against Plutella xylostella and Spodoptera litura was determined in labor, and the control effect against P. xylostella was assayed in fields. Results showed that the LC₅₀ value of spinosad against 3rd and 4th instar larva of P. xylostella is 1.965 0 mg/L and 3.675 6 mg/L. However, for the 3rd, 4th, 5th, 6th instar larva of S. litura, the value is 11.310 5, 229.769 1, 749.513 9, 4 817.303 0mg/L, respectively. Spinosad 10% SC has a good filed control effect against P. xylostella when the application dosage is 18.75, 22.50, 26.25 g/ha. The control effect of 1 d post-application is 21.08%, 44.27%, 71.32%, respectively.The control effect of 7 d post-application reached to 84.63%, 92.38%, 94.51%, respectively. Variance analysis showed that 3 d post-application, the control effect of 22.5 g/ha treatment is higher than 18.75 g/ha treatment, and lower than 26.25 g/ha treatment both at a 0.05 level. The toxicity of spinosad to P. xylostella is higher than S. litura,the reasonable application dosage is 22.5 g/ha.