Metal ion doping has been regarded as an effective strategy to improve photocatalytic activity of pristine photocatalysts for rapid charge transfer and separation effects achieved by doping induced defect states. We herein report the fabrication of uniform one-dimensional (1D) Sn4+-doped BiFeO3 (Sn-BFO) nanofibers (NFs) by a facile electrospinning technique with subsequent annealing treatment. Benefiting from metal ion doping and the unique 1D structure, the as-prepared Sn-BFO NF catalyst exhibits significantly enhanced photocatalytic performance on O2 evolution as well as improved photostability under visible-light illumination. Revealed by experimental investigation as well as density functional theory (DFT) calculation, the doped Sn atoms were incorporated into the BFO lattice and the band structure of BFO was effectively modified and the defect-related energy levels were produced, which leads to the boosted light absorption and improved charge transfer and separation efficiency. Additionally, an optimal Sn4+ doping percentage of 1.0% was discovered to achieve an average O2 evolution rate of 516.4 μmol h−1 g−1, nearly two times as much as the non-doped BFO samples.