Abstract: The objective of this experiment was to extracted and purified capsular polysaccharide from Staphylococcus aureus,and detected it is contents. Supersonic wave was used to crushed bacteria liquid, CTAB was used to combine capsular polysaccharide, CaCl2 decollement and ethanol precipitation of chemical method was used to extracte and purify capsular polysaccharide, phenol-vitriolic colorimetry was used to detecte its contents.The result showed that obtained capsular polysaccharide 0.31g,its contents was 65.06%. The result indicated that this experiment successed to extract capsular polysaccharide,and determined its contents, preliminary determined methods of crudely extracted capsular polysaccharide of Staphylococcus aureus.