Cerasus humilis is rich in calcium,rich in nutrition,and has immune function.Research on the preparation,structure and immunoregulatory activity of C. humilis polysaccharide (CHP) can provide basis for further processing of C. humilis.In this paper,the CHP was extracted by water extraction and alcohol precipitation method using C. humilis as raw material,and the extraction process was optimized by response surface methodology.The CHP was purified by DEAE-52 cellulose chromatography column and G-100 Sephadex gel column.The structure of CHP was characterized by high performance liquid chromatography,gel permeation chromatography and infrared spectroscopy,and the immunoregulatory activity of CHP was determined.The results showed that the optimal extraction process conditions of CHP were as follows:extraction temperature 79 ℃,extraction time 2 h,liquid-solid ratio 16∶1(mL/g).Under these conditions,the polysaccharide yield of dried C. humilis powder was (32.18±0.08)%.There were CHPP-1 and CHPP-2 in the purified C. humilis polysaccharide.The content of CHPP-1 and CHPP-2 were 99.16% and 99.33%,respectively.The monosaccharide composition and molar ratio of CHPP-1 were arabinose∶galacturonic acid∶glucose =51.4∶20.29∶17.36,molecular weight was 47.26 kDa.The monosaccharide composition and molar ratio of CHPP-2 were arabinose∶galacturonic acid∶glucose =41.81∶28.24∶11.68,molecular weight was 22.94 kDa.Both components were pyranoid ring polysaccharides.CHPP-2 can significantly enhance the proliferation of macrophages and effectively stimulate the release of NO,TNF-α,IL-6 and IFN-β.The CHP is rich in content and has strong immunomodulatory activity.