The effect of pyrethroids fenvalerate, cypermethrin, deltamethrin and Organic phosphate Insecticid dimethoate on the Aphis gossypii and its natural enemy, Leis axyridis was studied in 1984.Results show that the toxicity of fevalerate to the Leis axyridis is lower than those of cypernethrin, deltamethrin and dimethoate.During the Peak occurrence of Leis axyridis, the fevalerate is the best for controlling Aphis gossypii.The concentration of 30 PPm for fevalerate application is suitable.