Abstract: Flexible and transparent barrier films are in demand in the fields of organic solar thin-film cells,flexible organic light-emitting diodes,electronic paper and vacuum insulation boards.Flexible SiOxCyHz thin films were prepared on PET base films by the roll-to-roll method using HMDSO as monomer and O₂ as the reaction gas.SiOxCyHz thin films were prepared by plasma-enhanced chemical vapor deposition(PECVD)with a counter-electrode roller structure.The effects of film thickness,oxygen/monomer ratio and reaction vacuum on water permeability(WVTR)were studied.The composition,transmission spectrum and stress of the film were measured.The water permeability decreases with the increase of SiO CyHz film thickness,oxygen/monomer ratio,and decrease of pressure.When the thickness of SiOxCyHz film is 500 nm,the water permeability is lower than 5×10^-3g/(m²·day).The light transmittance(380-760 nm)of SiOxCyHz film reached 88.6%.The film surface was smooth,and the surface roughness was 1.8 nm.The stress of siloxane film increases significantly with the increase of thickness.