The invention relates to a recovery process and device for a dehydrating agent for waste acetone generated in alginate fiber filament production. The recovery process comprises the following steps of heating to distill a waste acetone mother solution from an alginate fiber filament dehydration tank to remove other organic components and impurities in waste acetone, and returning permeate to the alginate fiber filament dehydration step after separating heavy components through a ceramic membrane, wherein the heavy components are generated by heating distillation; inputting distillate to a preheater and an evaporator through a pump, enabling the distillate to enter a membrane separation unit in a steam way, obtaining an acetone product meeting a treatment requirement at an entrapment side of a pervaporation membrane separation unit, and enabling refined acetone obtained after dehydration to enter the alginate fiber filament dehydration tank to reused as a dehydrant; connecting the permeation side of the pervaporation membrane separation unit with a vacuum system, treating penetrated steam in a rectifying tower after condensing the penetrated steam by a penetrating fluid condenser, obtaining acetone with low water content at the top of the tower, enabling acetone to enter an acetone mother solution tank, and discharging wastewater from the bottom of a kettle. The recovery process disclosed by the invention is simple in course, high in safety factor, low in equipment investment, high in energy utilization ratio, small in floor area of the whole set of process and small in equipment height.