Abstract: AIM To study the structural property of the bioactive component from the fermentation broth of Streptomyces 139 which can inhibit IL-1R. METHODS Polysaccharide 139A is extracted and purified by means of macroreticular resin Diaion HP-20, cation exchange and DEAE Sephadex A-25 chromatography. The sugar compositions were analyzed with GC, the linkage positions of 139A were determined by methylation and GC-MS. RESULTS The bioactive component which can inhibit IL-1R is a kind of polysaccharides. CONCLUSION The components of 139A repeat units are conjectured.