In order to study the optimal extraction process of crude polysaccharides from Pleurotus eryngii, with fresh fruiting of Pleurotus eryngii as raw material, the influence of extraction time, solid-liquid ratio, and temperature, etc. on the extraction efficiency is analyzed using the hot water extraction method. Box-behnken design(BBD) is used for response surface analysis, and the optimal condition is as follows: extraction temperature of 47 ℃, extraction time of 4.9 h and solid-liquid ratio of 1∶19 (g/mL). Among the factors，the heating temperature has the greatest influence on the extraction rate, then the material liquid ratio, and at last the extraction time. Under this condition, the extraction rate of crude polysaccharide from Pleurotus eryngii reaches the maximum of 5.66% which is close to the actual verification value. Therefore, the optimization of the extraction condition of crude polysaccharides from Pleurotus eryngii by using response surface method is reasonable and feasible, and it provides a theoretical basis for the industrial application of crude polysaccharide extraction from Pleurotus eryngii using hot water.