From the viewpoint of molecular competition,a theoretical model was developed to investigate the effect of vacuum and temperature on the film refraction.It shows that with the increase of vacuum pressure the refractive index decreases,and with the increase of temperature the refractive index increases.Some ZrO2 films were deposited in different vacuum pressures and temperatures and the samples refraction indices were calculated.The results show that the experimental data are basically consistent with that from the model.