Objective: To investigate the inhibitory effect of Boschniakia rossica(BR) on rat precancerous hepatic foci induced by diethylnitrosamine (DEN) and its antioxidative activities. Methods: The expression of tumor markerplacental form glutathione S-transferase (GST-P), p53 and p21 protein were investigated by immunohistochemistry techniques using ABC method. TNF-α was measured by ELISA and antioxidative activities of SOD, MDA, GSH-Px,GST and CAT were investigated by colorimetric method in rat serum and mitochondria of liver cells. Results: The 500 mg/kg of BR-H2O extract fraction from BR-methanol extract had inhibitory effect on the formation of DEN-induced GST-P-positive foci in rat liver and the expression of mutant p53 and p21 protein was lower than that of hepatic precancerous lesions. The serum TNF-α was increased by the administration of BR extract in the early stage of chemical hepatocarcinogenesis in rat livers. The serum and liver cells mitochondria activities of SOD and GSH-Px rose again in rats administered with BR-H2O extract and the increasing activity of GST and content of MDA in the hepatic precancerous were decreased by the BR-H2O extract. Conclusion: These results indicated that BR-H2O extract has inhibitory effect on DEN-induced precancerous hepatic foci in rats and induced TNF-α production in rats. The antioxidative action was exhibited by the administration of BR-H2O extract in the early stage of chemical hepatocarcinogenesis in rat livers.