This study was performed to elucidate the effects of Gokajisilsosiho-Tang(GJST) on the lactic dehydrogenase(LDH) release, cell viability and activity, lipid peroxidation, DNA synthesis and the changes of total protein synthesis and GSH changes in vivo and in vitro in rat cultured hepatocytes from hydrogen peroxide$(H_2O_2)$-induced injury. The GJST extract had not an effect on cytotoxicity in all experimental results. The treatment of GJST extract of $160{mu}g/ml$, $320{mu}g/ml$ showed the significant effect to decrease LDH leakage induced by t-BHP in cultured rat hepatocytes. The higher concentration of GJST extract than $160{mu}g/ml$, showed the inhibitory effect on decreasing cell viability induced by t-BHP. The treatment of t-BHP to rat cultured hepatocytes resulted in a concentration dependent increase in TBARS, in the presence of GJST extract the production of TBARS induced by hydrogen peroxide was inhibited concentration dependently, significantly inhibited at $80{mu}g/ml$ of GJST extract and above. The GJST extract simutaneously present with t-BHP prevented the loss of total protein and GSH in a concentration dependent manner. These results suggested that GJST extract may play a hepatoprotective role in oxidative damage induced by hydrogen peroxide and a therapeutic potential of inhibiting liver injury.