We have successfully prepared Cu-Al-O thin films on silicon (100) and quartz substrates by RF magnetron sputtering method.The as-deposited Cu-Al-O film is amorphous in nature and post-annealing treatment in argon ambience results in crystallization of the films and the formation of CuAlO2.The annealing temperature plays an important role in the surface morphology, phase constitution and preferred growth orientation of CuAlO2 phase, thus affecting the properties of the film.The film annealed at 900℃ is mainly composed of CuAlO2 phase and shows smooth surface morphology with well-defined grain boundaries, thus, exhibiting the optimum optical-electrical properties with electrical resistivity and transmittance being 79Ω·cm and 80% respectively.The direct optical band gaps of the films are found in the range of 3.3-3.8 eV depending on the annealing temperature.