Abstract: To determine the composition and protective effect on Raw 264.7 cells of polysaccharide from Pseudostellaria heterophylla as a traditional Chinese medicinal, the main active ingredient-Pseudostellaria heterophylla polysaccharide (PHP) was extracted by water, precipitated by ethanol, and purified by anion exchange column chromatography. Gel permeation chromatography (GPC) and high performance liquid chromatography (HPLC) were used to determine molecular weight and monosaccharide composition of PHP. Ultraviolet spectroscopy (UV) and Fourier transform infrared spectroscopy (FT-IR) were used for primary structural characterization of PHP. Furthermore, the Raw 264.7 cell model was used to explore protective effect of PHP on Raw 264.7 cells induced by LPS. The results showed that the yield of crude polysaccharide of Pseudostellaria heterophylla was 8.23%, and the polysaccharide content was 51.47%. After purification by DEAE-52 column chromatography, the polysaccharide content increased to 80.52%, and the molecular weight distribution was between 500 to 92×10³ Da. The monosaccharide components of PHP include glucose, galactose, arabinose, mannose and glucuronic acid. Cell experiments showed that the safe dose of PHP was 80~640 µg/mL and could increase the survival rate of cells induced by lipopolysaccharide (LPS). At a dose of 640 µg/mL, the survival rate increased by 7.21%, and it was found that PHP could improve the morphology of Raw 264.7 cells. In summary, in this study the polysaccharides from Pseudostellaria heterophylla were purified, the structure of PHP was characterized, and it was preliminarily confirmed that PHP had potential protective effect on LPS-induced damage to Raw 264.7 cells. This laid the foundation for the follow-up exploration of functional activity, structure-effect and dose-effect of PHP.