AlOfilms have been deposited at room temperature on polyimide substrates using oxygen ion beam assisted pulse reactive magnetron sputtering system in which aluminium sputtering is simultaneous with oxygen ion beam irradiation. A set of samples were prepared at different oxygen content and film characterizations have been carried out using X-ray diffraction (XRD) for film crystallization, atomic force microscopy (AFM) for surface morphology, and X-ray photoelectron spectroscopy (XPS) for elemental composition measurements and chemical bonding states. The films are smoother and near stoichiometric aluminum oxide as oxygen content increases up to 86%. All films are kept in amorphous structure. The optical properties of the films showed sensitive with oxygen content. Transparent films of refractive index 1.63 are obtained with a deposition rate as high as 70.3 nm/min by 86% oxygen ion beam assisted, which is about 5 times than the films by conventional reactive magnetron sputtering.