Investigations on setting down the optimum conditions for running the synthesis of NaVO3 and HCl based on NaCl and V2O5 in the presence of steam at temperature point T = 823 K have been carried out. On the basis of these results, the optimum NaCl excess as compared to V2O5 in the reaction mixture and time of processing have been determined. It has been concluded that the conversion degree of V2O5 into NaVO3 is strictly connected with the granulometric composition of the reaction mixture.