Abstract: Virulence of avermectins 1.8% EC, 2% microcapsule suspension and chlorpyrifos 48% EC to S. zeamais and T. castaneum that lived in paddy ware tested by means of spraying in the laboratory. The results showed as follows: (1) The LD50s of avermectin 1.8% EC, 2% microcapsule suspension and chlorpyrifos 48% EC to S. zeamais were respectively 0.01mg／kg, 0.07mg／kg and 4.65mg／kg, and those of them to T. castaneum were respectively 0.08mg／kg, 0.50mg／kg and 5.89mg／kg. (2) The death rate of avermectin 1.8% EC to the two stored-grain insect pests was the highest among three kinds of insecticides in the same conditions. (3) S. zeamais was more sensitive to the three kinds of insecticides than T. castaneum. The recommended dosages of Avermectin 1.8% EC, 2% microcapsule suspension and Chlorprifos 48% EC are respectively 0.05mg／kg, 0.80mg／kg and 2.0mg／kg in order to control S. zeamais, and those of the three insecticides are respectively 0.05mg／kg, 0.80mg／kg and 8.0mg／kg in order to control T. castaneum.