The invention discloses a method for preparing a mixed sugar alcohol product by reutilizing an erythritol production mother solution, which comprises the following steps: diluting the erythritol production waste mother solution, adding activated carbon for sugar to perform decolorization, filtering with a nanofiltration membrane, desalting and decolorizing with an ion exchange resin, concentrating and crystallizing to recover erythritol, directly concentrating or decolorizing and concentrating the rest of mother solution, crystallizing the mixed sugar alcohol, returning the crystallization mother solution to recover the erythritol, reutilizing the rest of mother solution or initial mother solution, crystallizing the mixed sugar alcohol, and drying to obtain the mixed sugar alcohol product. The method can completely recover the effective components in the erythritol production mother solution, thoroughly avoids waste of the mother solution resources and emission of pollutants, and has wide application prospects.