Gallium-Aluminum doped Zinc Oxide (Ga-Al doped ZnO) thin films prepared on glass substrates by using facing targets sputtering methods. Electrical, structural and optical properties of Ga-Al doped ZnO thin film with various thicknesses were studied in detail. Crystal structure of the Ga-Al doped films was hexagonal wurtzite. Increased thickness of Ga-Al doped ZnO thin film, the resistivity decreased and crystallity improved. As the results, The resistivity of Ga-Al doped ZnO thin films with thickness of 500 nm exhibited 4.17x10(-4) Omega.cm and average optical transmittance of all thin films showed above 85% in the visible range.