The　nano-thickness　SiOx　deposited　on　polyethylene　terephthalate　(PET)　film　and　biaxially　oriented　polypropylene　(BOPP)　were　fabricated　by　plasma　enhanced　chemical　vapor　deposition　(PECVD)　in　a　radio　frequency　(13.56　MHz)　glow　discharge.　The　nano-coatings　were　characterized　by　using　Fourier　transform　infrared　spectroscopy　(FTIR),　atomic　force　microscopy　(AFM)　and　ultrasonic　atomic　force　microscopy　(UAFM).　With　AFM　and　UAFM,　the　topography　and　ultrasonic　amplitude　images　were　obtained.　In　particular,　the　UAFM　images　reveal　the　subsurface　defects　in　the　coating.　The　tensile　property,　contact　angle　and　OTR　of　the　PET　present　and　absent　of　the　SiOx　coating　were　investigated　experimentally　respectively.　The　results　can　show　that　the　SiOx　coating　can　improved　the　barrier　and　the　tensile　strength.