Abstract: A two-dimensional fluid model is developed to study the radio-frequency atmospheric-pressure Ar/O₂/SiH₄ discharges.The effect of gas composition on the densities of precursor particles and the uniformity of silicon dioxide film is emphasized.The simulation results show that the content of O₂ plays a decisive role in the whole discharge system.When the content of SiH₄ is constant,increasing the contents of O₂ can greatly increases the deposition rate and optimizes the uniformity of the film without changing the electron density.Although SiH₄ content significantly influencing the density of SiH₃O,it has little effect on the film properties.Note,when O₂ content is equal to SiH₄,the formation channel of SiH₃O particles is dominant and its density is high.When O₂ content is greater than SiH₄,SiH₂O generation channel will be dominate and its density is greater than that of SiH₃O.Meanwhile,the density of SiO₂ increases greatly,and it can reach 10¹⁷ cm^-3.Therefore,in the actual industrial preparation of largearea films,increasing the O₂ content is helpful to obtain high deposition rate and high quality films.