The best condition of ethanol extraction of Magnolol from drug" herbal medicine of promoted growth" assisted by ultrasonic wave was studied in this paper. The orthogonal design showed that the best ultrasound time, temperature, ethanol concentration and solid-liquid ratio were 60 min( three times and 20 min per time), 35℃, 65% and 1:10, respectively. Moreover, ethanol concentration was shown to be the most important influential factor among the investigated factors.