Chaenomeles speciosa fruits were extracted using water.The extracts were precipitated with 20%～95%(φ) ethanol,respectively.The amount of total polysaccharide was measured with phenol-sulfuric acid method.A method using high-performance size-exclusion chromatography(HPSEC) equipped with multiangle laser-light-scattering photometry(MALLS) and differential refractometry(RI) was presented for determining the molecular weight and molecular weigh distribution.RAW264.7 macrophage were cultured and stimulated with the polysaccharides in vitro and the production of nitric oxide in the cells was determined by the Griess assay.The aim of the study is to determine the amount and the molecular weight of the polysaccharides from Chaenomeles speciosa fruits,and preliminary investigate the immunomodulatory activity,The study provided the basis datas for the further research of Chaenomeles speciosa fruits.,and provided a simple and system method for the research of natural polysaccharide.The ethanol fractional precipitation showed that the order of total polysaccharide content was 95%＞80%＞40%≥60%＞20%.The results indicated that most polysaccharide from Chaenomeles speciosa fruits might be precipitated when ethanol concentration was up to 95%(φ) and the crude polysaccharide purity had risen from 35.1% to 45.0% when the concentration of ethanol increased from 20% to 95%.HPSEC-MALLS-RI system showed that all the polysaccharide samples had the similar compositions.They appeared three chromatographic peaks and the retention time were not apparently different.The Mw were 6.570×104 g·mol-1and 1.393×104 g·mol-1 respectively,and one less than 10 000 which was failure to obtain accurate values.The molecular weight of the first two polysaccharide distribution index(Mw/Mn)were 1.336 and 1.639 respectively.The polysaccharide samples had not exhibited immunomodulatory activity assessed on the basis of nitric oxide production by RAW264.7 macrophage cells in the experiment.