The invention relates to an extracting and refining method of water soluble polysaccharide in berry of nitraria tangutorum bobr, in particular to a method extracting the water soluble polysaccharide from the berry of nitraria tangutorum bobr, which is characterized by comprising the following steps: firstly, refluxing and extracting the berry of nitraria tangutorum bobr by using ethanol with concentration of 70-90 percent at 40-80 DEG C, and filtering the refluxed and extracted berry of nitraria tangutorum bobr to obtain filter residue; secondly, refluxing and extracting the filter residue by using distilled water at 60-90 DEG C, and filtering the refluxed and extracted filter residue to obtain extracting solution; thirdly, concentrating the extracting solution to be 1/10-1/5 of primary volume, adding 3-5 times of ethanol with concentration of 95 percent, settling for 12-24h at 4 DEG C, eccentrically eliminating supernatant fluid and getting precipitation, and cooling and drying the precipitation to obtain nitraria tangutorum bobr polysaccharide powder; fourthly, adding the distilled water to dissolve the nitraria tangutorum bobr polysaccharide powder, removing protein for 8-13 times by using a Sevage method; fifthly, leading the polysaccharide removed protein to be processed by macroporous resin column, eluting by using distilled water until eluent is air color and transparent; sixthly, collecting the eluent, concentrating, dialyzing, depositing in alcohol, getting precipitation, and cooling and drying the precipitation to obtain polysaccharide powder.