The　multi-layer　TiO2　nanotube　array　thin　films　have　been　formed　by　anodic　oxidation　method　via　adjusting　the　outer　voltage　during　oxidation　process　in　glycerol　electrolyte　containing　0.3%　NH4HF2.　The　diameter　of　the　nanotube　array　increases　with　the　outer　voltage,　and　the　length　of　nanotube　in　every　layer　increases　with　the　anodic　oxidation　time.　These　multi-layers　bring　new　possibilities　to　tailor　the　properties　of　the　TiO2　nanotube　array　thin　films　formed　via　anodic　oxidation　method.　Further,　such　multi-layer　structure　provide　a　new　approach　to　evaluate　the　growth　rate　of　TiO2　nanotube,　which　will　help　us　to　understand　more　deeply　the　formation　mechanism　of　the　TiO2　nanotubes.　The　growth　rate　of　TiO2　nanotube　array　is　respectively　1.2　and　3.6　mu　m/h　under　the　anodic　voltage　of　30　V　and　60　V.　These　multi-layer　TiO2　nanotube　array　thin　films　may　exhibit　lots　of　potential　applications　in　photoelectrochemical　fields.　(C)　2011　Elsevier　B.V.　All　rights　reserved.