Nickel oxide thin films have been prepared by direct current(DC) reactive magnetron sputtering from a metallic Ni target in an Ar and O2 mixed atmosphere. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been used for the study of the crystal structure and to detect binding energy of different chemical states. Scanning electron microscopy (SEM) observations reveal a dense fine-grained structure with the grain size about 10 nm. Both Ni2+ and Ni3+ ions exist in the NiOx films. The films exhibit anodic electrochromism, and the coloration and bleaching of NiOx film are associated with insertion and deinsertion of Li+, OH- ions and electrons in the NiOx film. In addition, electrochromic performance and response time of NiOx film have been investigated. Results indicate that the modulation range of the visible optical transmittance can reach 47%, the colored response time is 9 s, and the bleached response time is 1s.