A method for measuring Al 2O 3 optical wave guide film and studying its fabrication technique was proposed.The photon scanning tunneling microscope (PSTM) images of Al 2O 3 optical wave guide film made by ion beam enhanced deposition (IBED) technique at different temperature were analyzed.The results show that by properly increasing the temperature of the substrate,the scattering loss was decreased and the property of optical Al 2O 3 wave guide was improved.