TiO2　nanotube　array　thin　films　have　great　potential　in　many　fields,　such　as　solar　cell,　photo　catalyst,　photo-induced　cathodic　protection　for　metals　and　bioactivity.　In　order　to　investigate　the　formation　process　of　the　TiO2　nanotube　array　thin　films,　the　EIS　spectrum　and　current　density　were　measured　during　the　anodic　oxidation.　The　results　showed　that　the　formation　process　could　be　divided　into　four　stages.　The　current　density　decreased　sharply　at　the　first　stage,　and　then　increased　at　the　second　stage,　followed　by　declining　and　finally　remained　constant　value.　In　addition,　the　current　density　increased　with　the　anodic　voltage.　The　EIS　spectrum　varied　in　different　stage.　The　simulated　circuit　was　composed　three　sections,　the　first　sections　indicated　the　resistance　of　the　electrolyte,　the　second　one　gave　the　double　layer　structure　between　the　electrolyte　and　titanium　electrode,　the　third　one　was　a　inductive　loop,　which　represented　the　anions　absorbed　on　the　surface　of　the　TiO2　nanotube＇s　wall.　The　more　cations　were　absorbed,　the　higher　value　of　the　inductive　loop　would　be.　The　EIS　results　showed　that　the　value　increased　with　the　outer　voltage,　which　means　that　more　cations　were　absorbed　under　the　higher　anodic　voltage.