Abstract: AIM　To investigate the structures and immunomodulation activity of four homogeneous polysaccharides: LBP 1a-1, LBP 1a-2, LBP 3a-1 and LBP 3a-2 isolated from Lycium barbarum L. brought from Zhongning County, Ningxia Province. METHODS　Their molecular weights, sugar component (constituents) and their linkages were determined by gel permeation chromatography, acid hydrolysis, periodate oxidation and NMR spectrum. The activity of immunomodulation was evaluated with splenocyte proliferation by ［³H］-TDR incorperation, in vitro. RESULTS　Four polysaccharides with molecular weights 11.5×10⁴, 9.4×10⁴, 10.3×10⁴ and 8.2×10⁴, were shown to enhance splenocyte proliferation induced by ConA. LBP 1a-1 and LBP 1a-2 were α-(1→6)-D-glucans. LBP 3a-1 and LBP 3a-2 were found to be α-(1→4)-D-polygalacturonans. CONCLUSION　The four polysaccharides were first isolated from this plant. Polysaccharides with main chain of α-(1→4)-D-polygalacturonans showed stronger immunomodulation activity.