In this paper, the inorganic-organic thin film encapsulation layer was newly adopted to protect the organic layer from moisture and oxygen. Using the electron beam, sputter and spin-coater system, the various kinds of inorganic and organic thin-films were deposited onto the Ethylene Terephthalate (PET) and their interface properties between organic and inorganic layer were investigated. In this investigation, the SiON and Polyimide (PI) layer showed the most suitable properties Under these conditions, the WVTR for PET can be reduced from a level of 0.57 g/m(2)/day (bare substrate) to 1*10(-5) g/m(2)/day after application of a SiON and PI layer. These results indicate that the SiON/PI/SiON/PI/PET barrier coatings have high potential for flexible organic light-emitting diode (OLED) applications.