As a typical material for 1D flexible supercapacitors, the inherent low conductivity and under-utilized theoretical capacity of MnO2 hinder its further development in wearable energy textiles. Herein, the Fe-doped MnO2 nanowires (Mn/Fe-5%) with superior crystal structure and linearity were synthesized by one-step hydrothermal method. Benefiting from the crystal defects and oxygen vacancies induced by Fe doping, the Fe-doped MnO2 nanowires (Mn/Fe-5%) exhibited excellent electrical conductivity and specific capacitance. Moreover, by incorporating appropriate Fe3+ to balance the surplus protonation, the tunnel structures of MnO2 become more stable. On this basis, Fe-doped MnO2/rGO hybrid fiber electrodes were constructed by wet spinning and chemical reduction strategy for the first time. Notably, the Fe-doped MnO2 nanowires were blended up to 50 %, which can be attributed to the linear morphology and intercalation action of Fe-doped MnO2 nanowires. Finally, the symmetrical fiber supercapacitors were assembled with Fe-doped MnO2/rGO hybrid fiber as electrodes. Astonishingly, the fiber supercapacitors presented significant volume-specific capacitance of 203.7 F cm−3 at 1.75 A cm−3 (1.57 times that of the MnO2/rGO fiber supercapacitors and 2.4 times that of rGO fiber supercapacitors) and impressive energy density of 28.29 mWh cm−3. Besides, the assembled solid-state fiber supercapacitors distinguished excellent deformation stability and electrochemical output stability. This work points the way to the doping modification of nanomaterials, the convenient and fast construction of hybrid fiber electrodes, the further developments of fiber supercapacitors.