In this paper, vanadium oxide thin film of TCR of - 3.5%/K has been deposited by pulsed DC magnetron sputtering method. The property of this VOx has been investigated by X-ray diffractometer (XRD) and atomic force microscopy (AFM) in detail. XRD test indicates that this film is composed of V2O3, V3O5 and VO2.VOx microbolometer with infrared (IR) absorbing structure is fabricated based on porous silicon sacrificial layer technology. Optimized micro-bridge structure is designed and carried out to decrease thermal conductance and this structure shows good compatibility with micromachining technology. This kind of bolometer with 74% IR absorption of 8-14 μm, has maximum detectivity of 1.09×109 cm$Hz1/2/W at 24 Hz frequency and 9.8 μA bias current.