We measured the MDA content and CAT, SOD and GPx activities in the intestinal contents of the larval midgut tissue, and found that the MDA content showed a trend of decreasing–increasing–decreasing, which decreased at 6 h and 24 h after infection, respectively, and was significantly different from that at Bt0h, but the MDA content at Bt6h, Bt12h and Bt24h was lower than that at Bt0h. Here, CAT is linked to infection.