The present invention relates to a composition for preventing or treating cancer, comprising extracts of Anemone raddeana and Lonicera species containing a high concentration of antitumor saponins, and a method for preparing the same, wherein saponins contained in the extracts of Anemone raddeana and Lonicera species, are converted to anticancer saponins having high antitumor activity, thereby producing extracts containing a high concentration of the antitumor saponins, and the extracts thus prepared have been confirmed to show desirable antitumor activity. Accordingly, the extracts containing a high concentration of antitumor saponins of the present invention are promising for use in the development of drugs for cancer treatment.