Objective: To observe the inhibition effect of buckwheat polysaccharide (BP) on S180 sarcoma in vivo, and to explore its possible mechanism.Methods: Mice solid Tumor models and Mice ascites tumor models were established and divided into : model control group, buckwheat polysaccharide of high, medium and low-dose group (BP-H 400mg/kg, BP-M 200mg/kg, BP-L 100mg/kg), positive control - cyclophosphamide group CTX (150ug/ml), CTX+BP-M (200mg/kg+30mg/kg) group, 14 per group.The existed quality and existed time were observed dynamic, existence rate and tumor growth inhibition rate was calculated.Results: Compared with model control group and the CTX group, BP-H, BP-M and BP-L groups improved survival situations, increased survival time and survival rate of tumor mices.CTX+BP-M group is the best results; However, BP didnt significantly inhibit the growth of S180 sarcoma.Conclusion: The results suggested that the anti- tumor effect of BP was not obvious, but it could improve existence quality and prolong life span.