The　crystallization　of　amorphous　TiO2　nanotubes,　which　were　prepared　by　anodic　oxidation,　was　carried　out　by　a　water-assisted　method　at　low　temperatures.　The　crystalline　phase　and　the　morphology　of　TiO2　nanotubes　were　observed　by　X-ray　diffraction　(XRD)　and　field　emission　scanning　electron　microscopy　(FESEM),　respectively,　and　the　photocatalytic　activity　was　characterized　by　the　degradation　of　methylene　blue　(MB).　Results　show　that　TiO2　nanotubes　crystallized　by　a　water-assisted　method　at　50　degrees　C　for　4　h　exhibited　high　crystallinity,　a　preferable　nanotube　structure　and　therefore,　high　photocatalytic　activity.　Sucrose　was　added　to　the　aqueous　solution　as　a　carbon　source　for　preparing　C-doped　TiO2　nanotubes.　X-ray　photoelectron　spectroscopy　(XPS)　and　ultraviolet-visible　diffuse　reflectance　spectroscopy　(UV-vis　DRS)　were　used　to　observe　the　chemical　state　of　C-doped　TiO2　nanotubes.　After　C-doping,　the　crystalline　phase　and　morphology　of　TiO2　nanotubes　hardly　changed　but　the　bandgap　of　TiO2　was　narrowed,　which　endowed　TiO2　nanotubes　with　wide-range　light　absorption,　significantly　enhancing　the　photocatalytic　activity.　This　one-step　method　at　a　low　temperature　of　50　degrees　C　provides　a　new　pathway　for　preparing　C-doped　TiO2　nanotube　photocatalysts　with　enhanced　photocatalytic　activity.