Thin VOx films were prepared by magnetron sputtering onto p-Si(100) substrates. X-ray diffraction (XRD), atomic force microscope(AFM) and four-point probe method were employed to study the influence of the preparation parameters on the phase composition and resistance-temperature characteristic of VOx. The thermal stability of the films was also investigated. The results show that VOx films prepared by this method have relatively high temperature coefficient of resistance (TCR) and perfect thermal stability. They are promising to be used as thermal sensor materials in the microbolometer.