The brown planthoppers (Nilaparvata lugens, BPH) resistant to chlorpyrifos were selected in laboratory for eight generations. In the full course, the successive changes of activities of SOD, CAT and POD were analyzed. The analyses revealed that increasing of LD50 value was parallel to increasing of SOD, CAT, and POD, all of which increased gradually generation by generation. qRT-PCR showed that CAT was not directly involved in chlorpyrifos detoxification, but could be transcriptionally induced by chlorpyrifos. The results showed that the change of CAT activity was high correlated with chlorpyrifos toxicity in the full course, indicating that CAT played very important role in BPH antioxidant defense. It was suggested that the significant induction of CAT activity could contribute to enhancing antioxidant capacity in BPH and its population growth. CAT as an oxidative stress biomarker was recommended.