Abstract: Objective: To study the ultrasonic- microwave synergistic extraction of Bletilla striata polysaccharose and its antioxidant activity. Methods: Used polysaccharose yield as index,the liquid / solid ratio,immersion time,microwave power,extraction time were prescreened by single factor test.And the main factors levels were selected by orthogonal test design to optimize the best conditions of ultrasonic- microwave synergistic extraction technology.In vitro antioxidant activities of Bletilla striata polysaccharose were evaluated through the clearance abilities of hydroxyl radicals( ·OH) 、O_2~-· and DPPH·.Results: The optimum technological conditions were as follows: liquid / solid ratio 20∶ 1( m L / g),immersion time 6 min,microwave power 200 W,extraction time 5 min. Under the optimum conditions,the yield of lentinan was 6.98% ± 0.19%. The ultrasonic- microwave synergistic extraction technology was better than single ultrasonic extraction and single microwave extraction. Within the scope of the experiment,Bletilla striata polysaccharose had no obvious scavenging effect of O-2,but had good scavenging effect of ·OH and DPPH·.Bletilla striata polysaccharose,which was extracted with ultrasonic- microwave synergistic extraction,had higher scavenging activities of ·OH and DPPH· than that of microwave extractiontechnology. When the polysaccharose concentration of 0.5 mg / m L,the scavenging yields of·OH and DPPH·were92.82% and 74.21%. Conclusion: The ultrasonic- microwave synergistic extraction technology,which had many advantages such as saving time and high efficiency,was especially suitable for the extraction of polysaccharide substance.