Abstract: The effect of a traditional chinese medicine preparation(TCMP) on the change of enzyme activities, such as serum transaminase, hepatic antioxidant enzyme in eel（Anguilla anguilla） was evaluated in this study. Six eels, acting as Cupoisoned control fish, were exposed to waterborne Cu(0.12 mg/L) in moderately hard water for 4 days and kept at background Cu levels(0.004 mg/L) in the following 4 days. Eighteen eels were disposed in the same way as the Cu- poisoned control fish in the first 4 days, and then six eels among them were dipped in 200 mg/L water solution of Baogan Jiedu decoction(BJD), which was made up of Yinchen, Longdan, Gancao, Dahuang and Zhizi, in the following 4 days as low-dosage-drug-treated fish,other six eels were dipped in 400 mg/L BJD as high-dosage-drug-treated fish, and the remnant six eels were dipped in 100 mg/L of Jiangmeiling capsule containing Wuweizi as drugtreated control fish. Six eels as control fish were kept at background Cu levels(0.004 mg/L) in the whole trial course of 8 days without any disposition. The fish behavior and outer symptom were observed during the trial period. At the end, the fish were killed, and their blood were immediately collected and centrifuged to collect serum for testing the activity of its transaminase(AST and ALT).Subsequently, liver was dissected out, rinsed with doubledistilled water. A fraction of the liver was treated for the assaying of antioxidant enzymes(CAT,SOD and GSHPx). The results indicated that, compared with the control fish, the levels of ALT and AST were elevated significantly(P<0.01), the activities of CAT and GSHPx decreased sharply(P<0.01), and the activity of SOD was activated slightly(P<0.05) in Cu-poisoned control fish. And in drugtreated fish and drugtreated control fish, the activities of ALT and AST droped obviously(P<0.01), the activities of CAT and GSH-Px increased remarkably(P<0.01), the activities of SOD were enhanced further more than the Cu-poisoned control fish. Overall, these results as mentioned above demonstrated that the Baogan Jiedu decoction can enhance the activities of ALT and AST in the serum, and also bring the activities of CAT, GSHPx and SOD going up significantly. As a result, the preparation is suggested a effective liverprotective medicine against the liver injury induced by poison.