Abstract: In this study, six eels, acting as Cu-poisoned control fish, were exposed to waterborne Cu(0.12mg/L) in moderately hard water for 4 days and kept at background Cu levels(0.004mg/L) in the following 4 days. Eighteen eels were disposed in the same way as the Cu- poisoned control fish in the first 4days,and then six eels among them were administered by 200 mg/L water solution of Baogan Jiedu Tang (BJT), which was made up of Yinchen, Longdan, Gancao, Dahuang and Zhizi etc., in the following 4 days as low-dosage-drug-treated fish, six eels by 400 mg/L BJT as high-dosage-drug-treated fish, and the other six eels were administered by 100 mg/L of Jiangmeiling capsule containing Wuweizi as drug-treated control fish. Six eels as control fish were kept at background Cu levels (0.004mg/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, fish were killed, and then disseted anatomia-pathologically. Subsequently, liver was dissected out, rinsed with double-distilled water. A fraction of the liver was examined by transmission electron microscopy cytopathologiclly. The purpose of this study was therefore to determine the restoring-capacity of TCMP to the ultrastructure of hepatocyte in eel with liver injury induced by Cu-exposed. The results indicated that, ultrastructurally, the mitochondria of the liver cells swelled with disintegration and lyses of the cristaes. Rough endoplasmic reticulum expanded, intracisternal sequestration multiplied. The glycogen decreased and fat drops increased in the liver cells. Some nuclei of hepatocytes presented crenation degeneration. Compared with the Cu-poisoned control fish, the ultrastructure of hepatocyte of drug-treated fish and drug-treated control fish had restored notably. Overall, these results demonstrated that the TCMP could promote the mend of the ultrastructure of hepatocyte in the eel damaged liver. As a result, the preparation is suggested a effectively liver-protective medicine against the liver injury induced by poison.