Photoelectrochemical (PEC) water splitting using TiO2-based nanostructures is one of the most promising strategies for sustainable energy development. Here we reported Ti3+/Ni co-doped TiO2 nanotubes for high-efficiency PEC water-splitting. The co-doped photoanode was prepared through Zn reduction of Ni-doped TiO2 nanotubes grown on Ti-Ni alloy. Ti3+/Ni co-doping modified the energy band structure and narrowed the band gap to 2.84 eV, which enhanced optical absorption, increased the charge carriers, density and promoted charge separation-transport process. A remarkable solar to hydrogen conversion efficiency of 1.51% was achieved, which was about 10 times that of undoped TiO2. This work will facilitate developing novel co-doping approaches of Ti3+ species and other elements for enhancing PEC activity of undoped TiO2 nanotubes.