The Gallium-doped ZnO(GZO) film deposited at a temperature of 200℃ and a pressure of 10 mtorr has an optical transmittance of 89.0% and a resistivity of 2.0 mΩ·cm because of its high crystallinity. Effect of Al2O3 oxide buffer layers on the optical and electrical properties of sputtered ZnO films were intensively investigated for developing the electrodes of opto-electronic devices which demanded high optical transmittance and low resistivity. The use of Al2O3 buffer layer could increase optical transmittance of GZO film to 90.7% at a wavelength of 550 nm by controlling optical spectrum. Resistivity of deposited GZO films were much dependent on the deposition condition of O2/(Ar+O2) flow rate ratio during the buffer layer deposition. It is considered that the Al2O3 buffer layer could increase the carrier concentration of the GZO films by doping effect of diffused Al atoms through the rough interface.