Abstract: In this paper, the extraction process of burdock root polysaccharide was optimized using dynamic high pressure microfluidization (DHPM) combined with water extraction, and its infrared spectral structure and monosaccharide composition were analyzed to evaluate its scavenging activities against DPPH·, ·OH and ABTS^＋· radicals. The results showed that the factors affecting the yield of burdock root polysaccharide were DHPM pressure>extraction temperature>liquid to solid ratio>extraction time> number of treatments in descending order. The optimal extraction conditions were determined by response surface methodology: DHPM pressure of 148.0 MPa, liquid-solid ratio of 25:1 mL/g, two times of treatment, extraction temperature of 63 ℃ and extraction time of 1 h. Under these conditions, the predicted yield of burdock root polysaccharide reached 29.6%, and the relative error between the actual yield of 29.7% and predicted values was only 0.3%. The polysaccharides were mainly composed of fructose, glucose, arabinose, galactose and glucosamine hydrochloride, with molar ratios of 0.844:0.122:0.024:0.008:0.002. The polysaccharides of burdock root had different effects on DPPH·, ABTS⁺· and ·OH radicals. The IC₅₀ values were 0.30, 0.36 and 3.93 mg/mL, respectively. The study would provide a reference for the green and efficient extraction of burdock root polysaccharide.