Immunosuppression is the main source of ineffective treatment on tumor, and the study aimed to investigate the effect of artesunate on tumor immunosuppression.Supematants of re-cultivated Colon26 (murine colorectal tumor cells) after pre-treatment with or without artesunate were enrolled, and their effects on five immune parameters were assessed, including killing activity of natural killer (NK) and lymphocytes proliferation, as measured by MTT, and expressions of interleukin 2 receptor (IL-2R)α, CD3ε+ξ+ and CD3ε-ξ+ on lymphocytes, as analyzed by flow cytometry.Six immunosuppressive factors were measured by ELISA, including transforming growth factor (TGF) β1, vascular endothelial growth factor (VEGF), IL-4,IL-6, IL-10, and prostaglandin E2 (PGE2).