TiO(2)　nanotube　array　thin　films　were　prepared　by　put　Ti　substrate　into　0.5M　NH(4)HF(2)+1M　NH(4)H(2)PO(4)　aqueous　solution　via　anodic　oxidation　method　for　2h.　The　outer　voltage　used　in　this　work　is　respectively　5V,　10\7,　20V,　30V　and　40V.　The　as　anodized　TiO(2),　nanotube　thin　film　is　annealed　in　furnace　at　500　degrees　C　for　2h.　The　anatase　TiO(2)　nanotube　with　different　structure　could　be　finally　obtained.　The　variations　of　open　circuit　potential　with　time　at　light　irradiation　or　darkness　condition　were　investigated　in　this　paper.　The　results　show　that　the　open　circuit　potential　would　decrease　under　light　irradiation,　and　the　decrease　value　was　greatly　affected　by　outer　voltage　for　anodizing　and　could　be　reached　to　0.355V　with　the　outer　voltage　of　20V,　its　open　circuit　potential　shifted　from　0.065　V　to　-0.285V,　which　means　they　have　good　capability　for　cathodic　protection　for　metals.