The invention relates to the technical field of purification of chemical drugs, in particular to a recrystallization method of 
mirabegron and a preparation method thereof. The recrystallization methodof 
mirabegron comprises the following steps: dissolving a 
mirabegron crude product in a mixed 
solvent under a 
reflux temperature condition, cooling for 
crystallization, and collecting a 
solid; wherein the mixed 
solvent comprises an 
alcohol solvent and 
dichloromethane. According to the recrystallization method disclosed by the invention, by regulating and controlling the mixed solvent, the mirabegron in the beta 
crystal form can be rapidly converted into the alpha 
crystal form after being dissolved in the specific mixed solvent, the 
solubility of the mirabegron in the specific mixed 
solvent system is reduced after 
crystal transformation, and the mirabegron is slowly separated out, so that other 
impurity components are separated from the mirabegron, and the purification purpose is achieved;the method has the advantages of simple operation process, low production cost, reduction of the 
impurity imA content in the product especially for the imA 
impurity in the mirabegron crude product, simple 
crystallization and purification of the crude product obtained on the basis of the original process 
route, and important meaning for the research, development and application of mirabegron medicines.