Abstract: This study investigates the toxic effects of lambda-cyhalothrin on adult Monochamus alternatus (a vector insect of pine wilt disease) and the enzymatic responses under sublethal stress. Toxicity testing via the film method revealed significant time-dependent toxicity, with complete cessation of feeding activity observed at concentrations ≥ 50 mg/L. Using the surviving adults treated with the 72-hour median lethal concentration (LC₅₀) as the study subjects, enzyme kinetic analysis revealed that: cytochrome P450 enzymes (P450) play a dominant role in the detoxification pathway; glutathione S-transferase (GST) and carboxylesterase (CarE) activities showed initial induction followed by inhibition, and sustained inhibition, respectively; while key antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) reached peak activity at 48 hours of stress. This imbalance leads to a "polarized oxidative detoxification" reliant on a single pathway, ultimately resulting in oxidative collapse. In conclusion, this study confirms that lambda-cyhalothrin inhibits the survival of Monochamus alternatus through its time-cumulative toxicity and induced metabolic imbalance, providing a potential molecular target basis for vector control of pine wilt disease.