Abstract: OBJECTIVE To study the antitumor effects and immunological function of polysaccharide from Potentilla anserine L.(PAP) in vivo and in vitro. METHODS The SMMC-7721 cells were treated with different concentration of PAP. The effects of PAP on proliferation of human hepatoma SMMC-7721 cell were examined by MTT assay in vitro, and the relative results were fitted with mathematical model. The S180-bearing mice were intragastrically administered with 50, 100, 200 mg·kg^-1 PAP, respectively. The inhibition rate of S180 tumor and immunological function of PAP were measured in vivo. RESULTS The effects on proliferation of SMMC-7721 cell were correlated with the concentration of PAP in vitro. The highest inhibition was 43.57% at the dose of 400 mg·L^-1 PAP. The effects and PAP concentration were correlated and regressed. The inhibiting tumor rates were 46.41%, 52.29% and 59.48% in different groups treated with 50, 100 and 200 mg·kg^-1 in vivo, respectively. The T-lymphocytes and macrophage phagocytic index increased significantly after the effects of PAP in S180-bearing mice. CONCLUSION The compound PAP had significant activities of antitumor and immunological function.