In order to evaluate the anti-tumor and synergic effect of Soonkiwhajungtang with doxorubicin, the inhibitory concentration(IC), $IC_{50};and;IC_{90}$ of single use of doxorubicin and Soonkiwhajungtang with their concomitant treatment against Colon-26(Murine Rectum Carcinoma) was observed using MTT(Microculture Tetrazolium test) assay. In addition, their anti-tumor effects were also observed in the xenograft nude mice models agianst to Colon-26 cell lines. Soonkiwhajungtang has only mimic direct anti-tumor effect against to Colon-26 cell lines but they were decreased general depressed signs induced by implantation of tumor cell lines and increased the total WBC and lymphocyte numbers. So, it is considered or expected that Soonkiwhajungtang extracts were reduced the critical toxicity of doxorubicin and shows favorable synergic effect with doxorubidn and Soonkiwhajungtang extracts.