Abstract: The process conditions for extracting polysaccharides from Ipomoea batatas Lam.with the assistance of ultrasound were optimized by single factor and orthogonal array design methods.Using VC as a positive control, the antioxidant properties of polysaccharide from Ipomoea batatas Lam.were also studied by radicals scavenging of hydroxyl free radical (·OH) and superoxide anion free radical (O2-·) .Results showed that the optimal extraction conditions were determined as follows:extraction temperature 70℃, extraction duration 60min, material/liquid ratio 1:25 (g/mL) , and ultrasound power 350W.Under these conditions, the extraction yield of polysaccharide was 32.22%.The decreasing order of importance of the four process conditions affected polysaccharide extraction that were extraction temperature, extraction duration, material/liquid ratio and ultrasound power.The polysaccharide from Ipomoea batatas Lam.exhibited strong scavenging ·OH and O2-· abilities, and its radicals scavenging effect was weaker than VC.