Abstract: In order to isolate and purify pectic polysaccharide from Brassica rapa L.(BRP)in Xinjiang Uygur Autonomous Region,and study its composition and immunoactivity evaluation. In this paper,BRP was prepared by water extraction and alcohol precipitation and combined with different gel column chromatography. Physicochemical analysis showed that the carbohydrate content of the BRP was 78.86%±1.01%,the uronic acid content was 15.82%±1.05%,and the sulfuric radical content was 0.14%±0.05%,while the protein and total polyphenols were not detected. Fourier transform infrared spectroscopy(FT-IR)indicated that the BRP was pyranose containing both α- and β-configuration in the sugar units. The high performance gel permeation chromatography(HPGPC)analysis showed that the molecular weights of the BRP was calculated to be 838 kDa. PMP derivatives analysis indicated that the BRP was composed of rhamnose and galacturonic acid in a molar ratio of 1.94:98.06.The RAW264.7 cells model found that,when the concentration of the BRP was 12.5~100 μg/mL,it could significantly improve cell proliferation activity and phagocytic ability,and effectively stimulate the release of cytokines such as NO,TNF-α,IL-1β and IFN-γ. Furthermore,an immunoactivity of the BRP was concentration dependent. It indicated that the pectic of Brassica rapa L. in xinjiang Uygur Autonomocs Region had strong immunoactivity. Hence,it could be used as a natural immunomodulator in functional foods or medicines.