The invention discloses a method for extracting salvia plebeia polysaccharides through a supercritical CO2 fluid extraction technology. The method comprises the following steps: sequentially performing airing, grinding, soaking, re-grinding, supercritical CO2 fluid extraction, refined grinding, cold water extraction, filtering, alcohol precipitation and vacuum drying on fresh salvia plebeia leaves, and finally obtaining the crude polysaccharides. According to the extraction method disclosed by the invention, the salvia plebeia polysaccharides are prepared by using the supercritical CO2 fluid extraction technology, the total activities of the polysaccharides can be almost remained, any residue is not produced, and the operation is simple. Meanwhile, a sodium chloride solution is utilized for soaking before extraction, so that the extraction rate of the polysaccharides is improved; and the added trace fresh aloe juice achieves a synergistic effect with the salvia plebeia polysaccharides, so that the antibacterial activity of the salvia plebeia polysaccharides can be obviously improved.