Abstract: To investigate the toxicity of thiamethoxam, nitenpyram, and flonicamid against adults of Anisandrus dispar and their effects on the activities of detoxifying enzymes and protective enzymes, the indoor toxicity of 3 pesticides against A. dispar was determined using the immersion method. Adults were treated with sublethal concentrations (LC₅₀), and dynamic changes in the activities of glutathione S-transferase (GST), carboxylesterase (CarE), multifunctional oxidase (MFO), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were analyzed. The results showed that thiamethoxam had the best lethal effect（72 h LC₅₀ = 2.638 mg/L）, followed by nitenpyram （72 h LC₅₀ = 24.769 mg/L）, and flonicamid was the worst (72 h LC₅₀ = 486.482 mg/L). Among the detoxification enzymes, thiamethoxam and nitenpyram significantly induced stepwise increases in GST and CarE activities but inhibited MFO activity. Flonicamid continued to inhibit GST and MFO activities and initially increased CarE activity, then decreased it. Among the protective enzymes, thiamethoxam significantly increased POD and CAT activities, whereas flonicamid exhibited a phase-dependent inhibitory effect on SOD and CAT activities.