Abstract: In order to clarify the effects of imidacloprid and acetamiprid on the predation behavior and capacity of the natural predator of Orius sauteri, the female adult of O. sauteri was treated with the field recommended application dose by the method of residual film in glass tube, and the effects of these two insecticides on the predation behavior, predation amount, predation function response and searching efficiency were determined. The results showed that the predation behavior time of female adult was inhibited by the recommended application dose of imidacloprid and acetamidine. The searching, walking and predation time of female adult is significantly reduced by 100.0 and 332.5 s, 775.0 and 500.0 s, 1117.5 and 1145.0 s, respectively. The predation amount treated with imidacloprid and acetamidine was (4.89±1.36) and (3.56±0.73) eggs, respectively, which was significantly reduced by 1.55 and 2.88 eggs than that of the control. The predation of the female adult of O. sauteri on eggs of Heliothis assulta in the two treatments followed Holling type II functional response, while certain changes occurred in the parameters of the model. The predation efficiency (10.7363 and 7.0280, respectively) and search effect (0.6139 and 0.4021, respectively) of female adult of O. sauteri treated with imidacloprid and acetamidine was significantly lower than that of the control (26.1909 and 0.7929). In conclusion, the recommended field application dose of imidacloprid and acetamiprid presents negative effects on the predation behavior, and significantly reduce the predation efficiency and search effect of female adult of O. sauteri. The research might provide a theoretical basis for coordinating the scientific utilization of natural enemies and insecticides, and promoting the sustainable management of pests in tobacco fields.