Abstract: Fibrous root of Bletilla striata were treated as material and the extraction amount of polysaccharide was taken as the index. On the basis of single factor experiments,4 factors including the ratio of material to liquid,flash voltage,ultrasonic power and extraction temperature were selected as independent variables. Response surface methodology(RSM)was used to optimize the parameters of ultrasonic-flash synergistic extraction technology of polysaccharide from fibrous root of Bletilla striata. By establishing the subcutaneous tumor-bearing mice model,the anti-tumor effect of polysaccharides from fibrous root of Bletilla striata on S₁₈₀ tumor-bearing mice was observed after intragastric administration,and the levels of TNF-α and IL-2 in serum were determined. The results showed that the optimum extraction process of polysaccharide from fibrous root of Bletilla striata by ultrasonic-flash synergistic extraction technology was as follows:Deionized water was used as extraction solvent and the ratio of material to liquid was 1:21 g/mL,the flash voltage was 190 V,the ultrasonic power was 82 W,the extraction temperature was 62℃ and the synergistic extraction time was 60 s. The results of anti-tumor activity showed that the tumor weight of mice in three different dosage groups was significantly lower than that of model group(P<0.05,P<0.01). The results showed that the polysaccharide from fibrous root of Bletilla striata had a significant inhibitory effect on the tumor growth on S₁₈₀ tumor-bearing mice. The mechanism of anti-tumor might be that it could enhance the immune function by regulating the levels of TNF-and IL-2 in serum.