The invention discloses a method for purifying vildagliptin. According to the method, tetrahydrofuran is used as a solvent, an impurity disubstitution product is removed by virtue of a recrystallization method, and finally, the content of the recrystallization is decreased to 0.1%, so that the purity of vildagliptin is more than 99.8%, the quality of vildagliptin is improved, and reliable guarantee is provided for the improvement of quality of a vildagliptin drug.