The VOx thin films are successfully prepared on glass substrate by reactive magnetron sputtering at room-temperature, and subsequently annealed by rapid thermal annealing system in N2 from 0.5Pa to 10000Pa. The effects of annealing pressure on the optical performance and phase transition temperature (Tc) of VOx thin films are systematically investigated. The results show that the VOx thin films exhibit good performance with Tlum of 28.17%, ΔTsol of 12.69%, and Tc of 42. The annealing pressure had an obvious influence on the grain size, which can be attributed to light scattering effects by gas molecule. Compared with oxygen vacancy defects, the grain size plays a decisive role in the regulation of Tc. The restricting the growth of grain can be reduced the Tc, and a little deterioration effect on optical performance can be observed. In addition, the method in this paper not only depressed the Tc, but also simplified the process and improved efficiency, which will provide guidance for the preparation and application of VOx thin films.