The invention relates to an ultrasonic-assisted synthetic method of troxerutin. Ultrasonic is used for organic chemical reactions in a new form of energy, so that many reactions which cannot be carried out or difficult to carry out in the past can be carried out smoothly; the ultrasonic is greatly superior to the traditional stirring and external heating methods as a convenient, quick, effective and safe synthetic technique. After the ultrasonic is used for synthesizing troxerutin, the reaction time is only 45min, in contrast, the reaction time of the traditional liquid phase method is 90-120min, therefore, the reaction time of the ultrasonic technique is reduced by half; besides, the reaction temperature is reduced by 30-40 DEG C, the etherification rate is increased by 20%, and the etherification rate can be 95%. Furthermore, the ultrasonic technique is simple in process and easy for industrial production.