The radio-frequency magnetron sputtering-based plasma polymerization system has two benefits. First, it can be operated at low pressures (~10−1 Pa) to improve the quality of plasma polymer films. And second, it is a simple process to deposit SiOx:C/SiO2-like gas barrier multilayer thin films in a single chamber. The plasma polymer SiO2-like films are smooth and almost pinhole-free than SiO2 films by sputtering system. The gas barrier SiOx:C/SiO2-like multilayer thin films were deposited with hexamethyldisiloxane and oxygen flow by this system. The water vapor transmission rate (WVTR) of gas barrier films was measured by electrical calcium test. The WVTR value of three pairs multilayer thin films was 3.39×10−3 g/m2/day and the total thickness was only 450 nm. It reduced 40 percent thickness of the similar WVTR value (5 × 10−3 g/m2/day) of multilayer thin films at present.