The present invention relates to a process for producing a solid sodium diformate preparation having a formic acid content of at least 35% by weight based on the total weight of sodium diformate preparation, in which, at elevated temperature, an aqueous solution (E) is produced which comprises sodium formate and formic acid in a molar ratio of HCOOH:HCOONa of greater than 1.5:1 and which has a molar ratio of HCOOH:H2O of at least 1.1:1, the aqueous solution (E) is brought to crystallization to obtain a solid phase (F) and a mother liquor (G), and the solid phase (F) is separated off from the mother liquor (G), (i) the mother liquor (G) being fed to a distillation apparatus (DV); (ii) the mother liquor (G) in the distillation apparatus (DV) being admixed with a sodium-comprising base (A) to obtain a mixture (B) comprising sodium formate and formic acid; (iii) admixing the mixture (B) obtained from step (ii) with formic acid (D) to obtain the aqueous solution (E); and (iv) excess water (C) essentially being ejected only by withdrawal from the distillation apparatus (DV); and also to the use of a solid sodium diformate preparation obtainable by the inventive process as feed additive for animal feed, in particular for monogastric animal feed and especially for animal feed for hogs and/or poultry.