Method for extracting polysaccharide from Spirulina

The invention discloses a method extracting polysaccharide from Spirulina, which comprises the following steps: A. taking Spirulina alga powder, mixing with sterilized water in a ratio of 1:5, and boiling and extracting for 1 hour to obtain an extracting solution; B. filtering the extracting solution, and sending the filtrate into a centrifuge to remove slag, thereby obtaining a clear brown polysaccharide extracting solution; C. cooling the polysaccharide extracting solution to 10 DEG C below until the polysaccharide forms a precipitate in water, thereby obtaining a polysaccharide concentrated solution of which the weight concentration is 4-5 times; D. adding edible alcohol into the polysaccharide concentrated solution until the alcohol content reaches 80%, and precipitating the polysaccharide in the precipitation form; E. cleaning the polysaccharide precipitate with 80% alcohol twice for decolorization, thereby obtaining a creamy white Spirulina polysaccharide crude extract; and F. carrying out freeze-drying on the polysaccharide crude extract to obtain the finished product. The method is simple and economic, has the advantages of no environmental pollution, high extraction rate and high purity, and can enhance the polysaccharide yield.