Lignin was extracted from Acanthopanax senticosus remainders coming from pharmaceutical production process with acetone as extracting reagent. Lignin antioxidant capacity and yield were tested under singlefactor experiment,such as reaction temperature,reaction time,solidliquid ratio,acetic acid concentration,and solution concentration of acetone. The optimal conditions by a fourlevel orthogonal array design were as followings: reaction temperature 180 ℃, solution concentration of acetone 80%, solidliquid ratio 1∶20, and reaction time 80 min. The EC50 of the acetone organic lignin on DPPH was 1.518 mg/mL by verification experiments. The results indicate that the acetone organic lignin antioxidant capacity is better than that of Kraft lignin, but much lower than that of butylated hydroxyanisole (BHA).