This paper reported the activities and contents of antioxidant enzymes in blood serum and hepatopancreas from Cristaria plicata infected with Aeromonas hydrophila．For bacterial inoculation, the experimental group was injected with A. hydrophila (109 cell/mL) and the control group was injected with 0.9% NaCl solution. Blood serum and hepatopancreas were collected after 3, 6, 12, 24 h and 48 h for testing of the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) and of the contents of glutathione (GSH)，hydrogen peroxide (H2O2) and malonaldehyde (MDA). The results showed that there were significant differences in the activities of SOD in blood serum collected 3 h after injecting between experimental and control group; and the activities of GPX in blood serum also showed significant differences between experimental and control group at 12, 24 h and 48 h after injecting. The content of GSH in blood serum from the experimental group were significantly lower than that from the control group both at 24 h and 48 h after injecting, but in the hepatopancreas, GSH contents was significantly lower in the experimental group only at 24 h after injecting. The content of MDA in blood serum of experimental group was significantly higher than that of the control group at 6 h and 12 h after injecting. The content of H2O2 in blood serum and hepatopancreas respectively showed no significant differences between the two groups. In conclusion, infection of C. plicata with A. hydrophila would have more impact on the levels of antioxidant factors in blood serum than those in hepatopancreas.