The invention relates to a preparation method of 
coix seed 
polysaccharide. The preparation method comprises the following steps of: crushing and screening 
coix seeds first, and carrying out 
degreasing, water bath extraction, 
centrifugation, enzymolysis, concentration, 
alcohol precipitation and vacuum 
freeze drying and 
precipitation to obtain crude 
coix seed 
polysaccharide; and dissolving the prepared crude coix seed 
polysaccharide to obtain a crude coix seed polysaccharide solution, carrying out deproteinization, decoloration, 
dialysis and 
ion exchange 
chromatography on the crude coix seed polysaccharide solution to obtain purified coix seed polysaccharide, and then carrying out vacuum 
freeze drying to obtain 
white powder, namely the coix seed polysaccharide. According to the preparation method disclosed by the invention, the crude coix seed polysaccharide is extracted by using a 
water extraction and 
alcohol precipitation method, the crude coix seed polysaccharide is subjected to deproteinization, decoloration, 
dialysis and 
ion exchange 
chromatography to obtain the purified coix seed polysaccharide, and then, the purified coix seed polysaccharide is subjected to vacuum 
freeze drying to obtain the 
white powder, namely the coix seed polysaccharide; and therefore, the preparation method is simple and the coix seed polysaccharide is high in yield.