V-doped　TiO2　nanotubes　array　was　successfully　fabricated　on　a　Ti-V　alloy　via　an　electrochemical　anodization　process.　The　crystal　phase　and　surface　morphology　of　the　nanostructured　film　were　characterized　by　X-ray　diffraction　(XRD)　and　field　emission　scanning　electron　microscopy　(FESEM).　The　solution　diffusive　behavior　on　TiO2　nanotubes　was　investigated　by　electrochemical　impedance　spectroscopy　(EIS)　analysis　in　an　aqueous　electrolyte　containing　0.05　M　Na2SO3.　A　schematic　diagram　of　the　interface　solution　induced　into　nanotube　by　photocatalysis　on　V-doped　TiO2　under　visible　light　irradiation　was　proposed　in　the　study.　Considerable　photogenerated　holes　migrate　to　the　interface　of　TiO2/electrolyte　and　react　with　OH-,　forming　hydroxyl　radicals,　which　induce　the　electrolyte　into　the　nanotube　and　improve　the　hydrophilicity.　It　was　found　that　the　photoelectrocatalytic　reaction　of　TiO2　nanotubes　determined　the　diffusion　behavior　of　the　solution;　faster　diffusion　was　observed　on　the　V-doped　TiO2　nanotubes　array　under　visible　light　irradiation.　The　results　also　demonstrated　that　EIS　is　a　powerful　tool　for　characterizing　the　complicate　diffusion　behavior　within　the　porous　nanostructures.