BaTiO₃ fine powder was prepared by hydrothermal synthesis with various precursor materials selected in view of yield and reactivity. The effect of reaction temperature, time and raw material was investigated in the above process. While Ba(NO₃)₂ and TiO₂·xH₂O were used as starting material, it was not possilbe to prepare BaTiO₃ without mineralizer, however the same can be synthesized at 80 ℃ without mineralizer using Ba(OH)₂·8H₂O and TiO₂·xH₂O. The synthesis of BaTiO₃ was favored by higher pH of the reaction solution and conversion was found dependent on the reaction temperature instead of time. Experimental data suggested that BaTiO₃ seemed to be synthesized hydrothermally through reaction pathway that included dissolution of hydrous titania by nucleophilic attack of OH^- group in aqueous medium, nucleation by dehydration between Ba ion and titanium complex dissolved and the growth of nuclei.