Non-stoichiometric W₁₈O₄₉ nanowires and Ni-doped W₁₈O₄₉ nanowires （Ni-W₁₈O₄₉） were prepared by solvothermal method using WCl₆ and NiCl₂·6H₂O as tungsten and nickel precursor， PVP as surfactant and anhydrous ethanol as solvent. W₁₈O₄₉ and Ni-W₁₈O₄₉ nanowires were sprayed on the transparent conductive substrate of ITO-PET by atomization deposition method to obtain W₁₈O₄₉/ITO-PET and Ni-W₁₈O₄₉/ITO-PET electrochromic thin films. The experimental results indicated that the coloring/bleaching response time of W₁₈O₄₉/ITO-PET electrochromic film decreased from 16.5 s/8.2 s to 10 s/5.8 s by Ni doping. The coloring efficiency of W₁₈O₄₉/ITO-PET electrochromic films increased from 56 cm²·C^-1 to 74 cm²·C^-1 after Ni doping. Ni-W₁₈O₄₉/ITO-PET electrochromic films has a capacity retention of 70% after 1 500 charging-discharging cycles. Ni doped W₁₈O₄₉ could increase the contents of W⁵⁺ and oxygen vacancy， reduce the charge transferring resistance， and improve the electrochromic performance.