The preparation of barium titanate thin films on Ti substrates at low temperature using the hydrothermal process was studied. In addition, the interface relationship between film and substrate was investigated, revealing that the Ba-2+supercript stop ion diffused into the Ti(OH)(4) gel formed by Ti in a strong alkaline solution, resulting in a homogeneous film. A 3-level orthogonal array design was utilized to optimize the experimental conditions. The effects of preparatory conditions such as the barium-concentration, NaOH concentration, reaction time and substrate surface treatment were systematically studied. Results indicate that the effects of the NaOH concentration and substrate surface treatment are the significant variables influencing the relative crystal intensity (intensity of (110) BaTiO3 peaks in XRD spectrum/intensity of (001) Ti peak in XRD spectrum) of the films obtained. Polycrystalline, BaTiO3-films were obtained, with improved crystallinity and a dielectric constant of about 915 at 1 MHz.