The effects of different concentrations (0, 0.3, 0.6 and 0.9%) of fish feed additives (Hanbangchun and Olyukchun) utilizing effective microorganisms and herb medicine on activity of liver function were examined in olive flounder, Paralichthys olivaceus, Moreover, we investigated the characteristics of the additives. Total number of microorganisms (Lactic acid bacteria, Bacillus subtilis, Saccharomyces cerevisiae, Photosynthetic bacteria and Azotobactor) in the additives was 5.6${ imes}$10$^{8}$ CFU/g in the Hanbangchun and 3.0${ imes}$10$^{8}$ CFU/g in the Olyukchun. Levels of three typical pathological microorgamisms (Edwardsiella tarda, Vibrio anguillarum and Streptococcus sp.) in moist pellets (MP) were significantly decreased by the additives in a concentration-dependent way. Hepatosomatic index of fish in the 0.3% group was significantly increased. Total serum protein was increased in all the groups containing additives, but the protein content in liver was higher in the control group. Higher activities of catalase and superoxide dismutase which are involved in physiological defense mechanisms were found in the dietary groups containing 0.3% and 0.6%, respectively. These results suggest that the additives, Hanbangchun and Olyukchun, can increase tolerance of olive flounder against stress and hypoxic conditions by increasing activities of body antioxidant enzymes.