This study presents a novel approach to fabricating growth-controllable spindle-chain structured anodes for enhanced lithium/sodium storage. The authors developed a self-sacrificial template using Fe-based metal-organic frameworks (MIL-88A) through seed-mediated growth of Fe$^{3+}$ and fumaric acid in an aqueous solution. This method effectively separates the nucleation and growth stages, allowing precise control over the growth patterns of MIL-88A. The optimized spindle-chain structure of Fe$_2$O$_3$@N-doped carbon nanofibers (FO@NCNFs) enhances the anode's performance by improving structural diversity, ion/electron diffusion, and interface quality. FO@NCNFs exhibit excellent rate performance and long-term cycling stability, with a capacity of 167 mAh g$^{-1}$ at 10 A g$^{-1}$ after 2000 cycles for lithium-ion batteries (LIBs) and a sustained capacity of 260 mAh g$^{-1}$ at 2 A g$^{-1}$ after 2000 cycles for sodium-ion batteries (SIBs). This versatile method for fabricating bead-on-string architectures at both nanoscale and macroscale levels holds promise for developing high-energy-density and high-power-density electrode materials.This study presents a novel approach to fabricating growth-controllable spindle-chain structured anodes for enhanced lithium/sodium storage. The authors developed a self-sacrificial template using Fe-based metal-organic frameworks (MIL-88A) through seed-mediated growth of Fe$^{3+}$ and fumaric acid in an aqueous solution. This method effectively separates the nucleation and growth stages, allowing precise control over the growth patterns of MIL-88A. The optimized spindle-chain structure of Fe$_2$O$_3$@N-doped carbon nanofibers (FO@NCNFs) enhances the anode's performance by improving structural diversity, ion/electron diffusion, and interface quality. FO@NCNFs exhibit excellent rate performance and long-term cycling stability, with a capacity of 167 mAh g$^{-1}$ at 10 A g$^{-1}$ after 2000 cycles for lithium-ion batteries (LIBs) and a sustained capacity of 260 mAh g$^{-1}$ at 2 A g$^{-1}$ after 2000 cycles for sodium-ion batteries (SIBs). This versatile method for fabricating bead-on-string architectures at both nanoscale and macroscale levels holds promise for developing high-energy-density and high-power-density electrode materials.