Abstarct: The Eremurus plant, popularly called “serish” in Iran, belongs to the Liliaceae family. Eremurus spectabilis is one of the most important species from this genus. It grows very well in South and Central Asia, including Iran, West Pakistan, Afghanistan, Iraq, Turkey, Palestine, Lebanon, Syria and Caucasus. In current study a water-soluble crude polysaccharide (CESP) with molecular weight of 47.5 KDa was obtained from the roots of E. spectabilis by warm-water extraction (60°C), ethanol precipitation and deproteinization. CESP was purified with DEAE-cellulose A52 column and the main fraction was collected, vacuum-dried. The total yield of purified polysaccharide was 4.1% of the dried material. Total carbohydrate content and Specific optical rotation of polysaccharide were 97.2% and 36.6° respectively. Monosaccharide analysis showed that polysaccharide was composed of Glucose and Mannose with a relative molar ratio of 1.0: 2.9. Its structural features were elucidated by a combination of chemical and analytical methods such as methylation, Gc-Ms analysis, Periodate Oxidation and Smith degradation, Partial acid hydrolysis, FT-IR and 13C and 1H NMR Spectroscopy. The data obtained indicate that purified polysaccharide from E.spectabilis roots possessed a backbone of β-(1→4)-lixnked Glucose and Mannose with branched attached to O-6 by β- 1→lixnked Mannose.