In this paper, we report a fluorine-doped amorphous titanium dioxide nano-tube-array (a-TNT���F) catalyst for photo-electrochemical water splitting. The a-TNT���F can be activated by the full-spectrum sunlight with the advantages of high efficiency, low cost, easily prepared and rich natural sources. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and other tests confirm the nano-tube array structure of the a-TNT���F. The photo-electrochemical water splitting tests of a-TNT���F are conducted under the condition of dark, visible light and modulated sunlight. Results show that the water can be split into hydrogen and oxygen with the electrolysis voltage of 1.2 V under the irradiation of modulated sunlight, which is even lower than the theoretical voltage (1.23 V) of water splitting. The amorphous structure and doped fluorine greatly decrease the polarization of oxygen evolution on the electrode. The catalytic performance of the annealed a-TNT���F surpasses that of RuO2. We also ascertain the feasibility of combining a-TNT���F with solar cell for water splitting in natural environment. The a-TNT���F has great potential to be high performance catalyst for water splitting and has a bright future for large scale applications.