Abstract: The Al₂O₃ coatings were synthesized in the lab-built reactor by pulsed RF plasma enhanced chemical vapor deposition(RF-PECVD) on substrate of PET membrane,an advanced package material for organic electronic device.The influence of the pressure and deposition temperature on the permeation of oxygen and water-vapor was investigated with the advanced surface probes.The results show that the temperature and pressure had a major impact.To be specific,as the pressure increased at fixed temperature,the deposition-rate increased; as the temperature decreased,at fixed pressure,the deposition rate increased.Synthesized at the optimized temperature and pressure,the colorless,transparent,smooth,compact Al₂O₃ coatings(60 nm in thickness) on PET significantly increased the resistance against permeation of oxygen,water-vapor,and salt-fog.For example,its permeation of water vapor decreased by 1,000 times.