A new method of preparation of vanadium oxide films was reported.A thin VO x(x<2.5) film with good thermal sensitivity was prepared by ion beam sputtering of a V 2O 5 powder target and with a subsequent reduction annealing in mixing gas of N 2+H 2. The VO x(x<2.5) film has a negative temperature coefficient of resistance (TCR) of (-1~-4)%K -1 ,and an activation energy of 0.078eV~0.110eV. The relatively high TCR as well as low formation temperature shows that the film prepared by the new method is promising for application as thermal sensor material in an uncooled IR microbolometer.