Abstract: Bletilla striata polysaccharide has many applications and development prospects in medicine and food science. In this experiment, the polysaccharides from Bletilla striata were extracted by ultrasonic-assisted extraction method. The single factor experiment and orthogonal experiment were used to find the best conditions and then identified its structure. The traditional water extraction method and ultrasonic extraction method were used to compare antioxidant activity of Bletilla striata polysaccharide. According to the data, the optimal extraction process conditions were obtained: the ultrasonic power was 400 W, the ratio of material to liquid was 1:35 g/mL, and the ultrasonic time was 50 min. The yield of the polysaccharide was 8.18% + 0.04% under this condition. The scavenging rate of DPPH?and?OH of Bletilla striata polysaccharide by ultrasonic-assisted extraction method was higher than
by traditional water extraction method. The polysaccharides obtained by the two extraction methods showed no significant difference in ABTS+?clearance rate, and none of them had O2-?clearing ability.

Key words: Bletilla striata polysaccharide, Ultrasonic assisted extraction, antioxidant