Abstract: Compared to conventional methods of preparing protective films, the plasma polymerization approach is a more efficient, dry, and simple preparation procedure that allows the preparation of dense thin films with a thickness of hundreds of nanometers on a variety of substrates. In this paper, anti-atomic oxygen polysiloxane thin film were prepared on large-area flexible Kapton substrate by plasma-enhanced chemical vapor deposition （PECVD） . The effect of electrode spacing on the properties of anti-atomic oxygen polysiloxane thin film was investigated using SEM, AFM, FTIR and XPS. The results show that the reduction of electrode spacing accelerates the degree of monomer dissociation and the oxidation process of carbon-based components. With the decrease of electrode spacing, the deposition rate of the film increases, and the film transforms from organic-inorganic polysiloxane film （SiO_xC_yH_z） to inorganic film （SiO₂）. The increase of high dissociation energy Si-O bonds in the as-deposited films reduces the erosion rate of atomic oxygen of the films. This paper also establishes a technical foundation for the adjustment of the properties of other organosilicon functional films prepared by PECVD.