A water-soluble polysaccharide fraction from root of Potentilla anserine was obtained.  Gas chromatogram, FT-IR, physical and chemical characteristics of the Potentilla anserine polysaccharide fraction (PAPF) were analyzed.  The protective effects of PAPF against the H₂O₂ induced process of apoptosis of murine splenic lymphocytes were investigated in vitro.  Morphological assessment of apoptosis was performed with light microscope and laser scanning confocal microscope.  DNA fragmentation was visualized by agarose gel electrophoresis.  The amount of apoptotic cells was measured by flow cytometry.  The results showed that PAPF is composed of rhamnose, arabinose glucose and galactose.  H₂O₂ (200 μmol·L^–1) induced apoptosis of murine splenic lymphocytes with the cell volume reduced, cytoplasm and nuclear shrunk and DNA stained non-uniformly.  Condensed chromatin and formation of apoptotic body were observed in the apoptotic cells.  Apoptotic bodies in the cells treated with PAPF and H₂O₂ were less than those in H₂O₂ treatment alone.  DNA fragmentation assay showed that PAPF (50, 100, 200, and 400 μg·mL^–1) obviously reduced H₂O₂-induced ladder bands.  Flow cytometry analysis showed that H₂O₂ increased the populations of apoptotic sub-G₁ cells from 5.60% (control) to 45.40%, and PAPF decreased H₂O₂-induced apoptosis to 37.80%, 22.70%, 17.70%, and 8.50%, respectively.  In conclusion, PAPF reduced H₂O₂-induced oxidative damage in a dose dependent manner.