This paper measured the taching toxicities of the mixture information of Cypermethrin and Prothiofos against Setora postornata and Dendrolimus punctatus, picked out the better mixture information on the base of calculating their cotoxicity ratios, and controlled two kinds of the above mentioned insects by using the corresponding mixture emulsifiable concentrates and investigated the effects. The results showed that the mixture information with the ratio of 1 to 7 between Cypermethrin and Prothiofos had an obvious synergistic action, a lower cost and a good controlling effect on two kinds of insects in the field. 