The pineapple enzymatic technique was used to extract polysaccharides from shiitake mushrooms, with glucose serving as the standard for calculating the yield of the polysaccharides. The effects of acidity, alkalinity, extraction time, extraction temperature, enzyme dosage, and number of extractions on the extraction rate of mushroom polysaccharides were investigated under the control of a single factor. Orthogonal tests showed that the optimal process combination for the extraction of mushroom polysaccharides under the influence of multiple factors was pH 5, an extraction time of 1.5 hours, extraction temperature of 45°C, enzyme dosage of 0.8/100 g, and the number of extraction times of 3. The yield of mushroom polysaccharides under optimal processing conditions could reach 6.47%. The method is easy to operate, accurate, highly efficient, and it is a non-polluting and cost-effective process for extracting shiitake polysaccharides.