The invention provides a method for extracting isofraxidin from acanthopanax roots. According to the method disclosed by the invention, by virtue of extraction in combination hydrolysis in situ, glycosides prepared by binding isofraxidin and glucose, namely binding state isofraxidin, can be totally transformed into free state isofraxidin, so that the content of the isofraxidin in the extracting solution is increased, wherein an H<+> type ion exchange resin serves as a catalyst for promoting hydrolysis of the binding state isofraxidin, and a chlorinated solvent serves as an extraction agent forextracting the free state isofraxidin. Therefore, in the process of extraction in combination hydrolysis in situ, hydrolysis of the binding state isofraxidin and extraction of the free state isofraxidin are simultaneously completed. Moreover, the in-situ hydrolysis extraction method provided by the invention effectively avoids onerous two-step operations of hydrolysis and extraction, the operating procedures and the usage amount of the solvent are reduced, the production cost is low, and the yield of the isofraxidin is high.