Preparation method of red alga polysaccharide

The invention belongs to the technical field of extraction of algal polysaccharides, and relates to a preparation method of red algal polysaccharides, which comprises the following steps: by using redalgal plants as raw materials, washing the raw materials with water, carrying out alkali treatment, performing washing to neutrality, performing airing, performing pulverizing, adding propolis, extracting acid-soluble polysaccharides from the propolis by using a hot acid extraction method, and removing macromolecular polysaccharide components by alcohol precipitation, recovering ethanol from theresidual solution, performing cooling, performing filtering to remove propolis, filtering the filtrate with an ultrafiltration membrane, concentrating with a nanofiltration membrane, and performing freeze-drying to obtain the red alga polysaccharide. The preparation method of the red alga polysaccharides can effectively reduce the content of heavy metals in the red alga polysaccharides, and combines the technologies of red