Abstract: 【ABSTRACT】 BACKGROUND ＆ AIM: To investigate the effect of a traditional medicine, “qing gan hua yu” oral solution on phenotypes of hepatic precancerous lesion in rats. MATERIALS AND METHODS : A Solt_Farber two_step test model of prehepatocarcinoma in rat was established by diethylnitrosamine administration, to investigate the expression of γ_GT,G_6_P enzyme in different groups by enzyme_histochemisty，structure character of oval cell by electron microsocopy; the expression of AFP,ALB by immunohistochemistry. RESULTS: The concoction could prevent rat hepatic precancerous lesions by decreasing the expression of γ_GT and increasing the expression G_6_P enzyme. By electron microsocopy, we observed oval cells in model group were small with high nucleo_cytoplasmic ratio,while in treatment groups cells were larger and contained more rough endoplasmic reticulum. By immunohistochemistry,we found the expression of ALB was stronger in concoction group, although labeling for AFP was stronger in model group. CONCLUSION：The traditional medicine “qing gan hua yu” oral solution could prevent hepatic precancerous lesion rats,and was related to induction of rat hepatic oval cells to differentiate into mature hepatocytes.