Abstract: Objective In order to study rational complexing of insecticides and enhance killing2effect of complesed insecticids to resistant files.Methods The present paper is about killing-effect of complexed insecticide for resistant flies in laboratory by efficacy test and critera of public health insecticide for pesticide registration.Result The results shows that the effect of complexed insecticides to resistant flies in laboratory and in investigative spots are basically same.Conclusion Even if increasing the concentration and dosage of single insecticide,the killing-effect is less than the complexed insecticide.If the insecticides were complexed rationally,the killing-effect would be increased.This complexed insecticides in one of the main chemical method to control resistant lies,and it is also the main to deter and reduce the resistance of flies for insecticides producing and developing.