A thermal treatment below the crystallization temperature followed by rapid cooling down was adopted onto as-deposited BaTiO3 (BTO) amorphous films to freeze the microstructure activated at annealed temperature. A large increase of dielectric constant from 19 to 329 was observed at 0.1 Hz for the BTO film annealed at 600 °C for 60 min. Subsequently, three separated dielectric relaxations were exploited as a function of the frequency and temperature. Such dielectric responses were analyzed in terms of the activation energy. The evolution of oxygen vacancy with temperature can be invoked as being responsible for the observed dielectric relaxations.