Objective To observe the effect of Astragalus polysaccharides (APS) combined with cisplatin (DDP) on the expressions of Caspase-3 and Smac/Diablo in the mice with transplantated tumors Lewis lung carcinoma (LLC). Methods Ninety C57BL/6 J mice were randomly divided into normal control group, model group, and 50, 100 or 200 mg/L APS group, 6 mg/kg cisplatin group, and 3 mg/kg cisplatin combined with 50, 100 or 200 mg/L APS group; 10 mice per group. Except the mice in normal group, the rest mice were inoculated with LLC cells (1×10¹⁰/L) in the right fore axillary subcutaneous tissue to establish a model of tumorbearing mice. In the second day of building the animal model, the mice in the treatment group were given intraperitoneal injection of 0.3 ml of the drug. At the same time, the mice in the cisplatin group were given once a week, and the rest of the group mice once a day. The mice in the normal and model groups were given the same amount of saline injection for 20 days. All mice were killed on the 21st day. Tumor tissue lesions were observed by HE staining. The expression and location of Caspase-3 and Smac/Diablo proteins in transplanted tumor tissues were detected by immunohistochemical staining and image analys is method . Results The weights of mice were decreased in the 100 and 200 mg/L APS group and 3 mg/kg cisplatin combined with 50, 100, 200 mg/L APS group. Compared with the model group, the necrosis of tumor tissues in the 200 mg/L APS combined with 3 mg/kg cisplatin group was most obvious. The expression of Caspase-3 and Smac/Diablo was increased in the treatment group. The increasing of tumor tissues in 200 mg/L APS combined with 3 mg/kg cisplatin group was most obvious. Conclusion APS and APS combined with cisplatin restrain the growth of Lewis lung cancer in C57BL/6 J mouse, which may depend on increase of the expression of Caspase-3 and Smac/Diablo.