In order to investigate ecotoxicity effect of 2,4-dinitrotoluene (2,4-DNT) to freshwater fish(Brocarded carp), the acute toxicity test and the sub-lethal expriment were conducted in lab. The acute toxicity test show that 96h LC50 value of 2,4-DNT to Brocarded carp is 19.67 mg/L. Its toxicity rating is moderately toxic to fish. Based on the result of the acute toxicity test, fish was exposed to different concentrations (1/2LC50, 1/4LC50, 1/16LC50, 1/256LC50, surface water standard concentration) and killed at 3, 7, 10 and 14 day after exposure. The activities of Superoxide Dismutase (SOD) and Catalase (CAT) in liver tissue were analyzed. The results indicated the activities of SOD and CAT were inhibited from the third day in all treatment groups at post-exposure, they were lower than those of the control group (p＜0.01). The SOD and CAT activities of the control group were stable during 14-days. The CAT and SOD activities had the same changing trend and they were unstable under the pollution stress. The CAT enzyme was more sensitive than SOD enzyme under pollution stress. The results demonstrate that the SOD and CAT activities of liver in Brocarded Carp might be the promising biomarker of 2,4-DNT exposure to freshwater fish. Therefore it is suggested that the couple index of SOD and CAT could be used as biomarker of nitroaromatics compounds, when their pollutions affected living beings in aquatic environment.