A novel and industrially applicable strategy for separating and purifying the water-soluble polysaccharides from the fresh Spirulina platensis is introduced in this study. After hot water extraction, using chitosan flocculation treatment, 86.0% of the particles and 85.9% of the pigments in the crude extract were removed. The purity of polysaccharides could be increased to 94.6% and 96.1% by applying the macroporous resin ADS-7 to remove the impurities in the mode of static adsorption and in a dynamic mode of operation, respectively. The polysaccharides obtained were composed of three major components having molecular weights of 1400, 420 and 2 kDa.