In this article, the structural properties of Cynomorium songaricum Rupr. polysaccharide (CSP) after selenylation were investigated. The crude polysaccharide was obtained from C. songaricum Rupr. by water extraction followed by ethanol precipitation and freeze vacuum drying. Then selenylation of CSP has been accomplished by employing sodium selenite to modify the polysaccharide under the catalysis of nitric acid-barium chloride. After selenylation, the sugar content and the molecular weight increased but the protein content reduced. The maximum selenic content determined by ICP-AES was 2925 microg g(-1). The selenide CSP (Se-CSP) was characterised by the methods of UV spectra, FT-IR, Raman spectra and X-ray photoelectron spectroscopy. The results showed that the hydroxyl hydrogen of the sugar moieties was substituted by Se=O. Thermal stability of Se-CSP was also measured by TG-DTA.