The present invention relates to a preparation method of Mortierella sinensis mycelium polysaccharide, comprising: S1: Extraction of Mortierella sinensis mycelium polysaccharide: using Mortierella sinensis mycelium as raw material, ultrafine pulverization until the particle size is 7-11μm ultra-fine powder, added to water, soaked, then heated to boiling, kept slightly boiled, centrifuged, and the supernatant was obtained as the crude extract of Mortierella sinensis mycelia polysaccharide; S2: Concentrated to obtain a concentrated solution ; S3: precipitation: adding ethanol, stirring while adding, standing still, centrifuging, and collecting the precipitate; S4: drying: freeze-drying to obtain the polysaccharide of Mortierella sinensis mycelia. The method is simple, efficient, low in cost, high in polysaccharide yield and content, and suitable for large-scale production.