Transparent and hard Al2O3-SiO2 thin films have been deposited on PET substrate by E-beam evaporation with oxygen pressure ranging from 1×10-5 to 1×10-3 Torr at room temperature. Pressuredependent characteristics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), meanwhile, apparent transmittance and hardness of thin films were evaluated by uv-visible spectroscopy (UVs) and nanoidentor, respectively. The XRD results showed that the amorphous Al2O3-SiO2 film was obtained although the intensity of the broaden peak decreased with oxygen pressure increasing. The similar morphologies and composition were obtained in pressure range. Good apparent transmittance was found, which higher than 85% in the pressure range. Apparent hardness of PET was effectively improved from 2.77 to 5.7 – 6.1 GPa depending on oxygen pressure. However, the critical load of Al2O3-SiO2 film slightly decreased with oxygen pressure increasing.