Tea plant flower is a product of the tea plant during its growing. Polysaccharide are abundant in tea flower. However, the components in tea flower are underutilized at present. The study aimed at evaluating the antitumor activity and immunomodulatory effect of tea plant flower polysaccharide (TFP) via various in vivo assay systems. The inhibition effect of TFP on sarcoma 180 tumor (S180)-bearing mice was observed at dosages of 75, 150 and 300 mg/kg by systematically to measure the S180 tumor inhibition rate, mice survival rate and cellular immunity. The result showed that continuous administration of TFP for 10 day continuously was found to inhibit the growth of transplanted S180, prolong the mice survival days, promote the plasma interleukin-2, interferon-γ levels and improve the T-lymphocyte subsets CD4⁺ and CD4⁺/CD8⁺ percentages after treatment with TFP. In addition, TFP was found to increase the delayed-type hypersensitivity response and macrophage phagocytosis significantly. These results strongly suggest that TFP enhances the host defense response to tumor due in part to the immunomodulatory activity.