The present study was conducted to evaluate the hepatoprotective effect of puerariae Radix water extract an benzo(a)pyrene(B(a)P)-induced liver injuries in rats. In vitro experiment, primary cultured hepatocytes(5 × 10&^5 cells/ml) were cultured for 20-24 hours after adding Puerariae Radix water extract(32 ㎍/ml) and B(a)P(50 uM). In vivo experiment, Puerariae Radix water extract(0.25 g/kg/day, per os) was administered for 7 days and B(a)P(0.1 mg/kg/day, intraperitoneally) was given after the last administration of extract. And then the hepatoprotective effect of Puerariae Radix water extract was investigated biochemically through in vitro and in vivo experiments. Namely, activities of enzymms (GOT, GPT and LDH) were measured and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide(MTT) assay were carried out in vitro cell culture study and GOT, GPT, LDH and ALP activities and HDL-cholesterol, total cholesterol and triglyceride contents were performed in vivo study. In vitro experiment, Puerariae Radix water extract stimulated hepatocyte proliferation and significantly recovered enzyme activities (GOT, GPT and LDH) in comparison to group II administered B(a)P. In vivo experiment, Puerariae Radix water extract significantly decreased the enzyme activities(GOT, GPT, ALP and LDH in serum and ALP in tissue) and lipid contents(TC and TG) changed by B(a)P to normal level.