The invention relates to a process for preparing synthetic calcium fluoride (CaF2) (min 90 wt% CaF2) from fluosilicic acid. Said process includes the following steps: (a) reacting fluosilicic acid (H2SiFe) with ammonium hydroxide or ammonia in a first reactor (1) so as to obtain a first thick suspension, filtering said first suspension so as to obtain a filtrate containing an ammonium fluoride solution, (b) precipitating the ammonium fluoride solution, obtained in the form of a filtrate in step (a), with calcium carbonate in dry form or in the form of a suspension having a concentration of between 10 and 80 wt%, in a second reactor (3) so as to produce a second suspension containing the calcium fluoride and the ammonium carbonate, filtering said second suspension so as to obtain a filter cake containing calcium fluoride, and a filtrate containing an ammonia carbonate solution, washing and drying said filter cake so as to obtain calcium fluoride and a washing filter cake containing an ammonium hydroxide solution, wherein a portion of the second suspension, of from 10 to 70 wt%, is recycled to the second reactor (3) so as to enhance the crystallization of the calcium fluoride, changein most of the ammonia from the second reactor in step (b) due to partial decomposition of the ammonium carbonate under reactor conditions, then washing and sending said ammonia back into the first reactor, and collecting and treating, by means of distillation and condensation, the ammonium carbonate solutions obtained as filtrate and washing filter cake in step (b), so as to recover the liquid ammonia which is recycled to the first reactor (1).