Abstract: 【Objective】The purpose of the study was to clarify the sensitivity of Laodelphax striatellus (Fallén) popu-lations in different areas of Shandong Province to the new mesoionic insecticide triflupenzopyrim,and to investigate the effects of sublethal dose of triflupenzopyrim on the activities of protective enzymes and metabolic enzymes of L.striatellus,so as to provide theoretical basis for the scientific and rational use of triflupenzopyrim for the prevention and control of L.striatellus in the field.【Method】The indoor activities of triflumezopyrim to the 3^rd instar nymphs and adults of six L.striatellus populations fromYutai (rice),Yutai (wheat),Jiyang,Daiyue,Laiwu,and Changqing populationsin Shan-dong were determined by rice seedlings dipping method and topical application method,respectively.The effects of sub-lethal doses (LC₁₀ and LC₃₀) of triflumezopyrim treatments on the activities of three protective enzymessuperoxide dismutase(SOD),peroxidase(POD) and catalase(CAT)and three detoxification-metabolic enzymesglutathione S-transferase(GSTs),carboxylesterase(CarE) and cytochrome P450(P450)in 3^rd instar nymphs of L.striatellus were also compared.【Result】The results of rice seedling dipping method showed that the lethal median concentration (LC₅₀) of triflumezopyrim to 3^rd instar nymphs of L.striatellus ranged from 0.776 to 1.644 mg/L and to adults from 0.752 to 1.076mg/L.The results of topical application method showed that the median lethal dose (LD₅₀) of triflumezopyrim to 3^rd instar nymphs of L.striatellus ranged from 3.487×10^-4 to 7.441×10^-4µg/insect and to adults from 1.947×10^-4 to 4.196×10^-4µg/in-sect.The results of enzyme activity determination showed that the activities of SOD,POD,GSTs and P450 in L.striatel-lus were significantly increased after 72 h of treatment with 2 sublethal doses of triflumezopyrim of LC₁₀ and LC₃₀ com-pared with the control,but the CarE activity was significantly reduced (P<0.05,the same below),and there was a sig-nificant dose effect.The activities of CAT were increased in low dose (LC₁₀) of triflumezopyrim treatment and inhibited in high concentration (LC₃₀) treatment.【Conclusion】Triflumezopyrim has high insecticidal activities in contact and stomach toxicity against L.striatellus.L.striatellus populations in different regions of Shandong Province show high sensitivity to triflumezopyrim.L.striatellus can resist or reduce the toxicity of triflumezopyrim by increasing the activities of POD,SOD,GSTs and P450.