Nanocrystalline BaTiO3 with different crystal sizes were hydrothermally synthesized at different reacting temperature. Then the BaTiO3 nanopowders were sintered at various temperatures and BaTiO3 ceramics with different grain sizes. The dielectric constant, temperature and polarization were analyzed. Our experimental results showed that ceramic internal pore can influence stability of dielectric constant with frequency. Dielectric constant, dielectric loss and Curie temperature increase first and then decrease with reacting temperature. Small grain size of BaTiO3 ceramic reduce the Curie temperature. The dielectric loss peak was observed in the sample reacted at 240 ℃ and 270 ℃. This is mainly due to the oxygen vacancies in BaTiO3 sintered in a high temperature. The point defect also affected ferroelectric characteristics of the samples and lead double hysteresis loop.

hydrothermal method; BaTiO3 ceramics; dielectric properties; curie temperature；oxygen vacancy; double hysteresis loop