The work aims to further improve the barrier ability to oxygen and the feasibility of zinc oxide (ZnO) deposited composite film in food and pharmaceutical packaging materials. With ZnO and SiO2 as targets, ZnO/SiO2 composite films were prepared and deposited on PET substrates via RF magnetron co-sputtering. The influence of SiO2 on the microstructure and barrier ability of ZnO deposited film was analyzed in detail, and the preparation process of ZnO/SiO2 was optimized. The introduction of SiO2 changed the shape of ZnO nanoparticles from flaky oat to sphere. When the power density ratio PSiO2/PZnO was 0.67, the Ar flux was 20 mL/min and the deposition time was 20 min. When the work pressure was 0.5 Pa, the OTR of ZnO/SiO2 composite film decreased to 0.462 mL/(m2•d), and the WVTR increased to 0.367 g/(m2•d). The introduction of appropriate proportion of SiO2 can effectively improve the barrier ability of ZnO deposit to oxygen penetration, but when the amount of SiO2 introduced is too high, nano-cracks will intensify, which is unfavorable to the barrier ability of the composite film.