Abstarct: A new water-soluble polysaccharide with molecular weight of 184 kDa and specific optical rotation of +167̊ was extracted from the stems of Ephedra pachyclada by warm water method (70̊c). Purification of the polysaccharide was was done by DEAE-cellulose and sephacryl S-400 colum chromatography. The total suger of purified polysaccharide was 97.4% and there were no protein and polysaccharide were observed in it. The results of monosaccharides analysis was showed that purified polysaccharide E. Pachyclada stems was composed of Rhamnose, Arabinose, Xylose and Galactose with a relative molar ratio of 1.2: 1: 0.8: 2.6. Structure identification of polysaccharide was done by a combination of methylation, partial acid hydrolysis, GC-MS analysis, periodate oxidation and Smith degradation, FT-IR and NMR spectroscopy. And the result showed that the maine structure of purified polysaccharide wascomposed of (1→4, 1→4,6)-lixnked Galactose residues, with branches at o-6 it is structure consist of non-redusing terminal β-D-Galactopyranose residuse.