Abstract: The effects of Spinosad on tobacco beetles at different life stages and the detoxifying enzymes in larvae were studied by feeding tobacco beetles with tobacco leaves and flours containing different doses of Spinosad,and the larvae of tobacco beetles were treated with Spinosad solution of different concentrations.The results indicated that the contact and stomach toxicities of Spinosad to 5-instar larvae were weak,however at the concentrations of 5 and 10 mg/kg,Spinosad could completely inhibit the hatching of tobacco beetle egg and reproduction of adult tobacco beetle.The control effects of Spinosad at the concentrations of 5 and 10 mg/kg on tobacco beetles were 87.11% to 99.11% and 96.89% to 100% in 3 to 18 months after treatment,respectively.Moreover,Spinosad had obvious induction to the activity of carboxylesterase(CarE),glutathione-s-transferase(GSTs) and O-demethylase in tobacco beetle larvae,and also had certain effects on the kinetics constants,V_max and K_m,of carboxylesterase.