The invention discloses a method for preparing bendamustine hydrochloride freeze-dried preparation. In the method, the bendamustine hydrochloride is dissolved in medicinal ethanol first and then mixed with water-containing solution, and the mixture is stored at low temperature, so long-time contact between the bendamustine hydrochloride and water is prevented, and the hydrolyzation speed of the bendamustine hydrochloride is reduced because of the low-temperature storage. Moreover, for improving the situation that stable freeze-dried preparation with high re-dissolubility and beautiful appearance cannot be obtained by using organic solvent ethanol in the prior art, the inventor, through deep study, finds that the stable freeze-dried preparation with high re-dissolubility and beautiful appearance can be realized by using the safe medicinal ethanol. The bendamustine hydrochloride freeze-dried preparation prepared by the method has the advantages of low impurity content, low organic solvent residue content, high stability, beautiful appearance, high re-dissolubility and applicability to clinical application and industrial production.