Abstract: Objective To extract polysaccharide from radix rehmanniae preparata,and to study its immunity activity.Methods Polysacchayide extracted from radix rehmanniae preparata by water-extraction-alcohol-precipitation method was determined by phenol sulfonic acid spectrophotometry.SRBC and ovalbumin employed as antigens were injected into the mice.Three doses of radix rehmanniae preparata polysaccharide50,100,200 mg/(kg·d)were given orally for seven days.After the secondary immunization,the level of corresponding antibody and the concentration of the serum IL-2 were determined.Results The contents of polysacchar ide of samples was 1.45% and the average recovery was 98.53%.Standard curve was liner in the concentration range of 5~40 μg/ml.The levels of antibodies(anti-SRBC and anti-ovalbumin)and cytokines(IL-2)in median dose group of radix rehmanniae preparata polysaccharide were all significantly higher than those of control groups.Conclusion Radix rehmanniae preparata polysaccharide could enhance the immune function in normal mice.