Abstract: The toxicity and synergistic effects of seven insecticides and their mixtures to Phyllotreta striolata were tested by leaf-dipping method. The results showed that the toxicity of clothianidin was the highest, with LC50 value of 315.1 mg/L, and the toxicity ratio was 3.23-fold higher than that of dinotefuran. Thiamethoxam and lambda-cyhalothrin also had high toxicity to P. striolata, with LC50 values of 473.1 and 543.1 mg/L, respectively. The mixtures of clothianidin and lambda-cyhalothrin with ratios of 5:5, 4:6, 3:7, 2:8, 1:9 showed synergistic effects on P. striolata, with LC50 values of 215.6, 307.1, 334.1, 232.6, 240.7 mg/L, respectively, among which the 2:8 and 1:9 group showed the highest synergism, with co-toxicity coefficient of 203.9 and 210.5 respectively. Clothianidin and butene-fipronil mixed at the ratios of 5:5, 4:6, 3:7, 2:8 and 1:9 exhibited LC50values of 409.2, 356.9, 338.1, 402.4 and 392.6 mg/L, respectively, indicating most groups showed synergism against P. striolata except that of 5:5, and among which the 1:9 group showed the highest synergistic effect, with co-toxicity coefficient of 182.1. When the mixed ratios of clothianidin and monosultap were 5:5, 4:6, 3:7, 2:8, 1:9, the LC50values were 479.4, 540.0, 454.8, 737.0, 878.7 mg/L, respectively; the mixture at ratio of 3:7 showed synergism effect, with co-toxicity coefficient of 127.9, while others showed additive effects. The mixtures of clothianidin and lambda-cyhalothrin, butene-fipronil and monosultap, respectively, showed high synergism against P. striolata, suggesting they could be used to control the pest.