Abstract: By the method of toxicity bioassay, this paper studied the effects of different concentration (1.72, 3.44, 6.89, 13.77, and 27.55 mg·L^-1) Cd²⁺ on the activities of antioxidative enzymes (SOD, CAT, and GSH-PX) and the antioxidation substances (GSH and Vc) in hepatopancreas of freshwater crayfish Procambarus clarkii. The results showed that the SOD activity was induced at the lowest concentration (1.72 mg·L^-1) Cd²⁺ but inhibited at all other test concentrations Cd²⁺, and the inhibition degree was positively correlated with the Cd²⁺ concentration. Under all test concentrations Cd²⁺, the CAT activity decreased after an initial increase, with a peak 3 days after exposure. The CAT activity was sensitive to lower concentrations (≤6.89 mg·L^-1) Cd²⁺, but had no significant difference at higher concentrations (>6.89 mg·L^-1) Cd²⁺. When the Cd²⁺concentration was ≤6.89 mg·L^-1, the GSHPX activity showed a trend of increasing first and then decreased; when the Cd²⁺ concentration was 13.77 or 27.55 mg·L^-1, the GSH-PX activity was depressed during the first day of exposure. When the Cd²⁺ concentration was ≤6.89 mg·L^-1, the GSH content reached the highest value on the first day of exposure, and maintained at a higher level than the control group. However, when the Cd²⁺ concentration was ≥13.77 mg·L^-1, the GSH content had no significant difference with the control. The Vc content was very sensitive to all test concentrations Cd²⁺. It decreased significantly on the first day of exposure, with the decrement positively correlated to Cd²⁺concentration, but showed a recovering trend with exposure time. The results indicated that both the antioxidative enzymes and the antioxidation substances in the hepatopancreas of P. clarkii played important roles in coping with Cd²⁺ stress, and in most cases, showed a time and dosedependent relationship with Cd²⁺ concentration. The GSH-PX activity and Vc content of P. clarkii could be used as the potential bioindicators in evaluating Cd²⁺ contamination.