An improved process for preparing ammonium salts from fumaric or succinic acid, is described. The method consists of neutralizing the corresponding acid carbonate or ammonium bicarbonate at a molar stoichiometric or greater than the stoichiometric ratio of 4-5% in a saturated aqueous solution of the synthesized salt at a temperature not exceeding 40° C., followed by separation of the product and drying at a temperature not exceeding 70° C. After separation of the ammonium salts, the filtrate can be re-used. Isolation of the product is usually carried out by cooling the reaction mixture to a temperature of 15-18 C.°. The product comes out in almost crystalline form. Saturated aqueous solution of the synthesized salt is formed by the interaction of carbonate or ammonium bicarbonate with the appropriate acid at a temperature not exceeding 40° C. It is possible to obtain cleaner salt concentration weighing more than 99% and not yielding lower than 98%. The method allows for an increase in the yield of targeted products and ensures their consistent high quality due to their formation in crystalline form.