Thin barium titanate film was fabricated on Ti substrate by means of alternative current (AC) micro-arc oxidation (MAO) in Ba(OH) 2 alkaline solution. Using XRD, SEM EDS, and TEM, microstructure evolution during MAO and effect of heat-treatment on microstructure of the film were investigated. In 0.2 mol/l Ba(OH) 2 solution and current density of 2–5 A/cm 2 , combination of amorphous phases, cubic and hexagonal phases of BaTiO 3 exist in the as-prepared film. Some of cubic phases of BaTiO 3 are derived from amorphous phases during MAO. When annealed at above 900 °C for 8 h, the amorphous phases are crystallized. It is difficult to obtain tetragonal phase of BatiO 3 directly by AC MAO, even annealed at 1200 °C for 8 h.