Ba_0.5Sr_0.5TiO₃thin films were conducted by microarc oxidation and placing titanium plates as anode in 0 . 2 mol / L barium hydroxide & 0 . 2 mol / L strontium hydroxide aqueous solution. Phase composition, elements distribution, cross section structure and dielectric properties of the films were characterized. The results show that the films are composed mainly of tetragonal Ba_0.5Sr_0.5TiO₃phases. The distribution of Ba, Sr , Ti, and O element is uniform in dense layer in addition to micropore area. The film has excellent dielectric property, in the frequency of 1 kHz dielectric constant value is 411 . 3 . At last, the formation process of ferroelectric films deposited by microarc oxidation was analyzed, possible chemical reactions of the film’s growth were suggested.