Electrochromic NiO films were prepared by using an electron-beam deposition method. The influence of the preparation conditions, especially the substrate temperature, on the electrochemical stability of film was investigated. The optical properties and stability of as-deposited films strongly depended on the substrate temperature during deposition. The NiO film prepared at a substrate temperature of 150~$200^{circ}C$ was found to be the stabel when subjected to 5000cycles in a 0.5M solution of KOH between -6.0 and +0.8V. The best electrochromic parameters after 5000cycles were obtained for samples with substrate temperature of $150^{circ}C$. The obtained electrochromic parameters are CE=-0.049($lambda$=550nm), $Delta$OD=0.88($lambda$=550nm)$ extrm{cm}^2$/mC, Qin=-18.11mC/$ extrm{cm}^2$ and Qleft= 14.8mC/$ extrm{cm}^2$.