Abstract: An orthogonal array design was applied to optimize ultrasound -assisted extraction of antioxidant properties from Perrila frutescens. Three relevant factors that influence the antioxidant activity of the Perrila extract were investigated:ethanol concentration, extracting time and solid -liquid ratio. And the effect of each factor was estimated using deoxidization ability and elimination ratio of hydroxyl radicals as indicators. The results showed that optimal conditions for the extraction could be used 40% ethanol as extraction solvent with a solid -liquid ratio 1∶45g·mL-1 for 70min. Under this condition, the deoxidization ability and elimination ratio of hydroxyl radicals of extractions were the best with value at (1.21±0.021) and 22.49%±7.94%, respectively.