Abstract: Objective: To study the toxicity-decreasing and synergistic effect of total glucosides of paeony(TGP) on tumor-bearing mice treated by cyclophosphamide(CTX) for providing some valuable experimental data for searching high efficiency and low toxicity antitumor drugs and improving survival rate. Methods: S180 tumor cells were inoculated into healthy mouse to construct the S180 bearing-mice model,and treated with normal saline,TGP,CTX and TGP plus CTX respectively for 10 days,Observed live time to evaluate life extension rate for ascitic tumor,and measured tumor,spleen,and thymus weight to evaluate anti-tumor rate,index of spleen and thymus. Further more, lymphocyte proliferation rate and the plasma levels of tumor necrosis factor-α (TNF-α) were detected. Results: The high dose TGP significantly increased the survival time of mice bearing sarcosarcoma sarcoma S180 when compared with mice treated with normal saline,and decreased tumor weight and increased indexes of immune organs. TGP can strengthen anti-tumor activity of CTX,antagonize the inhibition of CTX on the body and immunologic system,and improve lymphocyte transformation and TNF-α level in plasma. Conclusions: TGP has inhibitory effects on the growth of tumor in S180 sarcoma-bearing mice and TGP can increase the activity of body immunity,improve the anti-tumor effects of CTX,and attenuate the toxicity of CTX as well.