A modified alkoxide-hydroxide sol-precipitation method, combining the sol-gel method and hydrothermal method, has been developed to synthesize monodispersed barium titanate with narrow size distributions. The key point of this method is the synthesis of ultrafine titanium hydroxide precipitate precursor by controlling the hydrolysis of Ti(OC(4)H(9))(4), where acetic acid and polyethyleneglycol were used to control the process. The as-prepared precursor and BaTiO(3) nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, high-resolution, BET specific surface area measurement, and scanning electron microscope. The monodispersed BaTiO(3) nanoparticles obtained by this method have an average size below 100 nm with a narrow size distribution.