Abstract: OBJECTIVE To explore the the anti-tumor and toxicity reduction effects of the bark extract of Sophora japonica on the CT26 tumor-bearing mice. METHODS BALB/c mice were used to establish CT26 tumor-bearing mice model. The model mice were divided into normal saline group, 5-fluorouracil(5-FU) group, combination group and the bark extract of Sophora japonica group. All groups were administered for nine days. During administration, change of mice's body weight were detected. After the end of administration, the tumor inhibition rate and the immune organ index was measured. Morphological changes in tumor and liver tissues were observed by HE staining. The levels of interleukin-2(IL-2) and tumor necrosis factor-α(TNF-α) in serum were measured by ELISA. The expression levels of Ki-67 in tumor tissues were detected by immunohistochemistry. RESULTS The tumor inhibition rate of 5-FU group, combination group and the bark extract of Sophora japonica group were 77.02%, 81.75%, 46.62%, respectively. Compared with normal saline group, the bark extract of Sophora japonica group significantly decreased the tumor weight, and significantly increased the immune organ index, IL-2 and TNF-α levels in serum(P < 0.05 or P < 0.01). The results of HE staining showed that the necrotic areas of tumor tissues in the the bark extract of Sophora japonica group were significantly increased. Immunohistochemical results showed that the number of Ki-67 positive cells was obviously decreased in the bark extract of Sophora japonica group. Compared with the 5-FU group, the weight loss and hepatocyte edema in combination group were reduced. CONCLUSION The bark extract of Sophora japonica possesses anticancer effect on CT26 tumor-bearing mice and has protective effect on weight loss and hepatocyte injury of mice induced by 5-FU chemotherapy.