Abstract: Nostoc sphaeroides kützing riches of polysaccharide and has special biological and physiological activity. The paperdo the reaserch of the extraction and seperation of Nostoc sphaeroides kützing to get fine Nostoc sphaeroides kützingpolysaccharide. Nostoc sphaeroides kützing is first crashed,dispored of color and fat,extracted then precipitated protein by sevagemethod. Precipitating polysaccharide with alcohol,then raw polysaccharide can be got with a success of centrifugal protocol.Inthe end,white water-soluble and brown alkila-soluble Nostoc sphaeroides kützing polysaccharide can be seperated by vacuumfreezing drying.FR-IT proves that the water-soluble and alkila-soluble Nostoc sphaeroides kützing have the common traits ofsom polysaccharide. The best extracting parameter of water-soluble is extracting 4 times with water (1:90) at 90℃for 6h each4 times. The best extracting parameter of alkila -soluble is extracting 4 times with NaOH (1:25,1mol/L) for 6h each 4 times. Thebest exacting ratio is 5.70%.

Key words: Nostoc sphaeroides kützing, water-soluble polysaccharide, alkila-soluble polysaccharide, seperation