NOVELTY - A nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber consists of a surface layer coated on carbon fiber having a diameter of 30-70 nm. The surface layer contains single-wall or multi-wall carbon nanotubes having a diameter of 0.9-100 nm, coated with anatase titanium dioxide particles having a diameter of 1-100 nm. The nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber comprises (in wt.%) nano titanium dioxide (0.05-25), carbon nanotubes (0.05-30), and carbon fibers (45-99.9).    USE - Nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber is used for dye-sensitized solar batteries.    ADVANTAGE - The nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber has one-dimensional continuity, high specific surface area, and excellent solution absorption property, light diffusion-reflection property, flexibility, workability, and strength. The nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber provides dye-sensitized solar batteries having excellent photoelectric conversion efficiency.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of nano-titanium-dioxide-coated-carbon-nanotube-reinforced carbon fiber, which involves dissolving 0.5-20% carbon fiber precursor polymer in a solvent to prepare a carbon fiber precursor polymer spinning solution, adding carbon nanotubes (0.01-10) and surfactant (0.001-3), ultrasonically dispersing, transferring the obtained spinning liquid to an electrostatic spinning device, carrying out electrostatic spinning at a spinning voltage of 10-35 kV, a flow rate of 0.01-5 ml/hour, and a spinning distance of 5-25 cm to obtain carbon-nanotube-reinforced carbon fiber precursor polymer, carbonizing the fiber in a carbonization furnace to obtain carbon fibers having a diameter of 30-700 nm, impregnating with a mixed solution of isopropanol and water in a volume ratio of 1:1, washing, drying in a vacuum drying box, and oxidizing to form the surface layer.