【Background】The parasitoid Aphidius gifuensis Ashmead is one of important natural enemies to control the population of the aphid Myzus persicae(Sulzer) in the fields. The chemical insecticides should infect the parasitoid and reduce its control effect when they were sprayed to control aphids or other pests. In order to avoid spraying insecticides during the sensitive period of A.gifuensis, it is necessary to know the insecticide toxicities and effects on different developmental stages. 【Method】Toxicities of four insecticides (5% avermectin, 5% alpha-cypermethrin, 10% acetamiprid, 10% imidacloprid) on adult parasitoids of A.gifuensis were evaluated under laboratory conditions by the methods of residual film in glass tube and feeding. The influences of four insecticides on the emergence rate of A.gifuensis were studied at sublethal concentrations of tobacco aphids. 【Result】Both the contact toxicity and the stomach toxicity of avermectin for adult parasitoids were the strongest among these insecticides, with mortality rates at 24 h reaching 87.78% and 94.44% respectively. The toxicity of imidacloprid were the weakest, with mortality rates at 24 h of 41.11% and 61.11% respectively. The toxicity of alpha-cypermethrin (81.11%, 86.66%) and acetamiprid (64.44%, 67.78%) were medium. The emergence rates could be significantly reduced when parasitoids were treated by avermectin and acetamiprid during egg stage or any of these four insecticides during the larval stage. However, the emergence rates were not changed distinctly when pupal parasitoids were treated. The sex ratio of parasitoid was significantly affected only when abamectin was used at the larval stage. 【Conclusion and significance】The mortality rates of parasitoids were higher when these insecticides were used at the adult stage, suggesting the insecticides should not be used during the presence of adult A.gifuensis in the field.