In this paper, ITO films with the oxide buffer layers were deposited by magnetron sputtering technique onto the PES. The oxide buffer layer was formed by a radio frequency (RF) magnetron sputtering method, using SiO2 or TiO2 target. The ITO layers were deposited by a low-frequency (LF) magnetron sputtering technique onto PES/Buffer layer. The sheet resistances of ITO films with the oxide buffer layers grown onto PES substrate were investigated as a function of time in the air and the vacuum. In both cases, the increasing rates of the sheet resistance of the PES/Buffer layer/ITO films are lower than those of the PES/ITO films. In addition, the increasing rates of sheet resistances of the films with the TiO2 buffer layer are lower than those of the films with the SiO2 buffer layer.