Abstract: The toxicity of pyridaben, acetamiprid and their mixtures to Bemisia tabaci (Gennadius) biotype B were tested using tube residual film, the efficacy of them were measured on tobacco plants, and the safety evaluation to tobacco were also measured. The results showed that acetamiprid showed the biggest toxicity in the three neonicotinoid insecticides, LC50 was 7.1195 mg/L, the mixtures of pyridaben and acetamiprid 1:1 and 2:1 showed some antagonism, and the mixtures of pyridaben and acetamiprid 4:1 and 8:1 showed additive effect, LC50 were 1.6103 and 1.1452 mg/L; The joint toxicollogical of Acetamiprid and Chlorpyrifos at the two ratio of 1:4 and 1:8 had great synergism, with the co-toxicity coefficient were 135.68, 177.16, respectively. The efficacy results were that the mixture of pyridaben and acetamiprid 8:1 (1 000 dilution) had the better efficacy, the defense efficacy was 89.6%~95.8% during 3 to 10 days. The safety evaluation results showed that the mixture of pyridaben and acetamiprid 8:1 1000 dilution showed a slight phytotoxicity to some tobacco plants, but had no effect on growth and development.