The aim of the present paper was to investigate the synergistic effect and mechanism of anticancer activity of Zuojinwan ( ZJW) comprising Coptis chinensis Franch ( HL) and Evodia rutaecarpa (Juss.) Benth ( WZY) at a ratio of 6 : 1 (w/w). In vivo anticancer activity testing was carried out by inhibiting the growth of S180 tumor. Tumor growth inhibition, spleen index, lymphocyte proliferation, apoptosis, tumor necrosis factor-alpha (TNF-alpha) level, activities of serum tumor markers (TMs), increase in life span (ILS), histopathology and gene expression were tested. The results indicated that ZJW could significantly induce apoptosis of cancer cells. The inhibition ratio, ILS and TNF-alpha levels of mice treated with ZJW were 50.54 %, 64.91 % and 1.04 ng/mL, respectively, much higher than HL and WZY when singly used. Furthermore, the activities of acid phosphatase and alkaline phosphatase were significantly increased and the activities of creatine kinase, aldolase and lactate dehydrogenase were reduced in serum, and the expressions of Bax and wild-type p53 proteins were much higher for the mice treated by ZJW compared with HL and WZY single-treatment groups. A clear synergistic effect on the anticancer activity was observed with ZJW, and the mechanism of antitumor growth may be due to an effect on gene expression and activities of tumor markers in serum.