The invention discloses a preparation method and a production device for producing a recycled fiber spinning solution with using a solvent, which comprises two or more vertical wiped film evaporators (3, 4, . . . ) connected with a single horizontal cylindrical kneading reactor. The aqueous mixture of cellulose and solvent and auxiliary agent is prepared into a spinnable cellulose spinning dope, which is characterized by injecting the material mixture into two or more vertical wiped film evaporators and a horizontal cylindrical kneading reactor, each unit is preferably equipped with a separate condensing system, and the vacuum system can be separately configured to share a vacuum system.