Ag-modified,　composite　TiO2　nanotubes　were　synthesized　using　molten　alkali-hydrothermal　method　under　an　ambient　atmospheric　pressure.　The　organization　and　morphology　of　the　composite　TiO2　nanotubes　were　characterized.　Nanotubes　have　clear,　uniform　and　neat　morphology　with　diameter　of　around　3　to　5　nm,　each　nanotube　composed　of　3　to　5　layers　and　wall　thickness　of　around　0.5　nm.　In　particular,　TiO2　and　Ag　nanoparticles　clearly　adhere　in　between　nanotubes　and　at　the　exterior　surface　of　nanotubes.　XRD　results　display　that,　the　composite　TiO2　nanotubes　from　the　single　anatase　phase　to　the　anatase　and　rutile　mixed　phase.　The　band-band　transition　occurs　within　a　wavelength　span　of　350　nm.　SPS　(surface　photovoltage　spectroscopy)　and　FISPS　(electric　field-induced　surface　photovoltage　spectroscopy)　demonstrate　the　bound　exciton　sub-band-gap　transition　characteristics　from　its　asymmetric　changes　corresponding　to　changes　in　polarity　of　the　external　electric　field.　Ag　modifing　has　imposed　considerable　influence　on　both　the　photovoltaic　response　of　composite　TiO2　nanotubes　and　the　separation　of　photoinduced　electrons　and　holes　at　the　surface　of　nanotubes.