The　electrochromic　NiO　films　were　prepared　on　ITO　conductive　glass　substrate　by　pulse　electrodeposition.　The　microstructure,　morphology　and　composition　of　NiO　films　were　investigated　by　X-ray　diffraction,　scanning　electron　microscopy　and　energy　dispersive　spectrum.　The　optical　properties　of　films　were　measured　by　UV-visible　spectrophotometer.　The　electrochemical　properties　of　films　were　analyzed　using　cyclic　voltammetry.　The　effects　of　Co　addition　on　the　electrochromic　properties　of　NiO　films　were　studied.　The　results　show　that　Co　addition　can　optimize　the　surface　morphology　of　NiO　films.　The　homogeneous　nano-mesoporous　microstructure　can　be　observed　on　the　surface　of　Co-doped　NiO　films.　Thus,　the　Co　addition　can　improve　the　electrochemical　activity　and　enhance　the　transmission　modulation　of　NiO　films.