Abstract: The extract process of total polyphenol from Polygonum viscosum was optimized and the antioxidant activity of total polyphenol in vitro was evaluated.Ethanol concentration, solid to liquid ratio, and extrction time were chosen as the independent variables using ultrasonic-assisted extration method.The optimum technological parameters of ultrasonic-assisted extraction for total polyphenol from P. viscosum were studied via the orthogonal experiment. Finally, the optimal extraction conditions were obtained: extraction temperature 30 ℃, ethanol concentration was 50% ( v/v) , the ratio of solid to liquid was 1 ∶ 50, ultrasonic time was 25 min, and extraction times were 2 times. It was found that the total polyphenols content from the P. viscosum was ( 94.6 ± 0.15) mg/g, average recovery rate of total polyphenol was 100.07%, variation coefficient was 1.00% ( n = 5) .The antioxidant activity was determined though 1, 1-Dipheny l-2-picrylhydrazyl free radical ( DPPH·) scavenging rate and total antioxidant activity test.The results indicated that the antioxidant activity of total polyphenol in P. viscosum was stronger than that in tertiary butylhydroquinone ( TBHQ) , and the EC50value ( 5.5 μg/m L) of DPPH· scavenging rate from P.viscosum was better than the EC50value ( 18.0 μg/m L) of TBHQ. Total polyphenol in P. viscosum is a natural antioxidant and free radical scavenger.