The invention discloses a method for preparing an ammonium fluoride with high purity, comprising the following steps: adding ammonia or liquid ammonia in an ammonium fluoride solution with the mass concentration of 8-50% to react for 10-60min; subsequently adding barium hydroxide into the solution; filtering and separating the silicon dioxide, barium sulfate and barium hexafluorosilicic acid deposition wherein to obtain the filtrate of ammonium fluoride solution; heating and concentrating the filtrate under the vacuum degree of -0.092-0.030Mpa and the temperature below 25-106 DEG C for 36-65min; stopping heating after the solution suddenly crystallizes; transferring the crystallized ammonium fluoride solution into a crystallizer; controlling the crystallization temperature at -10-25 DEG C; carrying out solid and liquid separation on the ammonium fluoride after the crystallization, thus separating the ammonium fluoride filtrate; and drying the obtained ammonium fluoride crystal under the temperature of 60-95 DEG C, thus obtaining the ammonium fluoride product with high purity after the drying processing. The method has the advantages of high product purity, low production cost and meeting higher requirement.