The invention relates to a method for continuously preparing phellinus igniarius mycelium polysaccharide, belonging to the technical field of bioengineering. The method comprises the following steps: extracting degreased phellinus igniarius mycelium in 95-DEG C hot water under reflux for 8 hours, centrifuging, concentrating, precipitating with ethanol, removing proteins, dialyzing, and carrying out freeze-drying to obtain water-extraction phellinus igniarius mycelium polysaccharide; dissolving the water-extraction residue in a 1% ammonium oxalate solution, extracting at 95 DEG C under reflux for 8 hours, centrifuging, concentrating, precipitating with ethanol, removing proteins, dialyzing, and carrying out freeze-drying to obtain acid-extraction phellinus igniarius mycelium polysaccharide; and dissolving the acid-extraction phellinus igniarius mycelium polysaccharide in 1.25 mol / L sodium hydroxide and 0.05% sodium borohydride solution, extracting at normal temperature for 3 hours, centrifuging, concentrating, adding acetic acid, precipitating with ethanol, removing proteins, dialyzing, and carrying out freeze-drying to obtain alkali-extraction phellinus igniarius mycelium polysaccharide. The phellinus igniarius mycelium polysaccharide continuously prepared by the method has obvious free-radical removal capacity and antioxidation activity. The preparation method is simple and easy to implement, is low in cost, can implement large-scale production, and can be used for other fungus mycelia, such as ganoderma lucidum, aweto, Grifola frondosa and the like.