3,4-Dichloroaniline (DCA) and its analogs are widely used as chemical intermediates in the synthesis of herbicides, azo dyes, and pharmaceuticals. They bring danger to growth, development, and propagation of aquatic organisms. The purpose of this study was to show DCA-induced oxidative stress response in liver of crucian carp (Carassius auratus). Superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO), and NO synthase (NOS) in liver were measured in crucian carp after exposure to DCA solution (0.2, 0.4, and 0.8mg/L, respectively) for 15 days and compared with the control. DCA significantly induced SOD activity and enhanced MDA concentration in liver of crucian carp. Compared with the control, GSH and NO concentrations decreased and NOS activity was inhibited in crucian carp liver 15 days after DCA treatment. The data suggested that DCA-induced free radical generation and antioxidant depletion, and caused oxidative stress and lipid peroxidation in liver of crucian carp.