The work aims to provide a method for preparing protective and functional silicon oxide coatings which can be widely applied in the field of vacuum decoration, and provide guidance for selecting coating process parameters in specific applications. Silicon oxide coatings with different microstructures were prepared at low temperature by changing O2/HMDSO ratio adopting PECVD technology. Surface and sectional morphology of the coatings was observed by scanning electron microscope. Microstructures and composition of the coatings were analyzed by X-ray diffractometer, Fourier transform infrared spectroscopy, X ray photoelectron spectroscopy and Raman spectrum. Optical transmittance of the coatings was characterized by UV spectrophotometer. Mechanical properties and wettability of the coatings were characterized by nanoindentor and contact angle meter, respectively. The coatings had smooth surface and compact structure. With the increase of oxygen flow ratio in reaction gas, the coating structure gradually transformed from SiO to SiO2, and a small amount of amorphous carbon structure existed, optical transmittance and hydrophilicity increased while mechanical properties decreased. When the carbon content was the lowest, the coatings exhibited the best transmittance and hydrophilicity, the transmittance in the whole visible light waveband was nearly 100%, and water-coating contact angle was 45.38°. When the carbon content was the highest, the coating exhibited the best mechanical properties, hardness was 13.5 GPa, and H/E was 0.11. PECVD can be used to obtain optically transparent silicon oxide coatings which feature in high hardness and surface cleaning convenience at low temperature. Microstructure and properties of the coatings can be adjusted through as control, so that the coatings can be applied to functional decoration applications which propose different requirements.