Chemotherapy damages immune system and has a lot of side effects. In this study, we investigate the function of Shenfu injection to reduce these unfavorable effects induced by chemotherapy on mice bearing Lewis lung sarcoma. Mice inoculated with Lewis lung sarcoma cells were divided into five groups: Lewis lung sarcoma control group, cyclophosphamide (CTX) group, and Shenfu injection (high, moderate, and low dose) + CTX group. After a 14-day treatment, the counting of peripheral blood cells, CD3+, CD4+, and CD8+ T lymphocytes were done, immunoglobulin (Ig) was measured, coefficients of spleen and thymus were calculated, and spleen T cell proliferation was evaluated in vitro. The CD4+/CD8+ and CD3+ T cells in high- and moderate-dose Shenfu groups were more than the CTX group (p < 0.05); spleen T cell proliferation of mice in high-dose Shenfu + CTX group is more prominent than the CTX group (p < 0.05); coefficients of spleen and thymus, WBC, and platelet (PLT) counting of mice in the CTX group were lower than control and high and moderate dose Shenfu + CTX groups. The level of serous IgG and IgM of all test groups shows no significant difference. Shenfu injection can improve cellular immune function and reduce myolosuppression of mice delivered with chemotherapy.