The present invention relates to a method for preparing an herbal composition with increased fat-soluble polyphenols, an herbal composition prepared by the method, and a use of the composition. The herbal composition with increased fat-soluble polyphenols of the present invention is characterized by the significantly increased content of fat-soluble polyphenols including decursin, compared with the herbal composition of comparative example, and also demonstrates a significant anti-oxidative activity, immune cell activating effect, and cancer cell growth inhibitory effect, significantly reduces renal toxicity and liver toxicity induced by the anticancer agent cisplatin back so as to be almost normal condition, and significantly inhibits the intestinal crypt loss caused by irradiation, compared with the herbal composition of comparative example. Therefore, the herbal composition with increased fat-soluble polyphenols of the present invention can be effectively used as a composition for cancer treatment, an anti-cancer adjuvant, a composition for enhancing immune function, a composition for protecting a living body, and a composition for preventing side effects of cancer treatment.