In this study, we report a high efficiency photocatalyst synthesized by Mn2+ doped ZnO nanofibers (NFs) fabricated by facile electrospinning and a following annealing process, in which Mn2+ successes incorporate to ZnO NFs lattice without changing any morphology and crystalline structure of ZnO. The photodegradation properties were studied for ZnO doping with different concentrations of Mn2+ (5, 10, 15 and 50 at.%). The 50 % Mn2+-doped ZnO NFs owns excellent active photocatalytic performance (quantum efficiency up to 7.57 %) compared to pure ZnO (0.16 %) under visible light and can be considered as an efficient visible-light photocatalyst material. We systematically analyzed the catalytic mechanism and showed that the enhancement belongs to the Mn doping effect and the phase junction between MnO and ZnO. The dominant mechanism of Mn doping leads to the presence of impurity levels in the band gap of ZnO, narrowing the optical band gap of ZnO. In addition, doped Mn2+ ions can be used as electron traps that inhibit the recombination process and promote electron-hole pair separation. Overall, this paper provides a facile approach to fabricate a highly efficient visible-light photocatalyst using controlled annealing.