Abstract: The purpose of this study is to solve the problem of slow kinetics and dependence on expensive platinum-based catalysts for cathode oxygen reduction reaction （ ORR ） in fuel cells. The core purpose is to develop a high-performance, low-cost non-noble metal alternative catalyst. In order to achieve this goal, a chlorine （ Cl ） doped Fe single atom catalyst （ Fe-CNCl ） was successfully prepared by introducing sodium chloride （ NaCl ） into the zeolite imidazole framework material （ ZIF-8 ） as the precursor and using the strategy of freeze-drying assistance and high-temperature pyrolysis, and systematically compared with the undoped control sample （ Fe-CN ）. The main methods used in the study include material synthesis, structural characterization and performance testing. In the synthesis, by combining the iron source with ZIF-8 and introducing NaCl as the Cl source, the target catalyst was obtained after high temperature pyrolysis and pickling. In terms of characterization, X-ray diffraction （ XRD ）, scanning / transmission electron microscopy （ SEM / TEM ）, X-ray photoelectron spectroscopy （ XPS ） and synchrotron radiation X-ray absorption spectroscopy （ XAS ） were used. The electrochemical performance was evaluated by rotating disk electrode （ RDE ） and rotating ring disk electrode （ RRDE ） in alkaline electrolyte （ 0.1 mol/L KOH ）. The research process and results show that Cl is successfully incorporated into the catalyst. XRD and electron microscopy analysis showed that the catalyst maintained the dodecahedron framework of the precursor after pyrolysis, and the iron existed in the form of atomic dispersion without forming clusters or particles. XPS and XAS analysis further revealed that the introduction of Cl formed a coordination bond （ Fe—Cl ） with Fe, breaking the high symmetry of the original Fe—N₄ site and forming an asymmetric local coordination structure. Electrochemical tests show that Cl doping greatly optimizes the ORR performance. The half-wave potential （ E_1/2） of Fe-CNCl is as high as 0.903 V （ vs. RHE ）, which is significantly better than that of undoped Fe-CN （ 0.854 V ） and commercial Pt / C catalyst. Its Tafel slope is lower （ 88 mV / dec ）, indicating faster reaction kinetics. Through the RRDE test calculation, the electron transfer number is close to 4 （ 3.9 approximately ）, and the hydrogen peroxide yield is extremely low （ 1.3% approximately）, indicating that the reaction efficiently follows the four-electron path and directly generates water. In the constant potential stability test for about 70 h, the current decay rate of Fe-CNCl is only 6%, showing excellent durability far exceeding the contrast sample （ Fe-CN decays by 25%, Pt / C decays by 31% ）. In summary, this study successfully constructed a high-performance Fe-C-N single-atom ORR catalyst through a simple Cl element doping strategy. This work not only demonstrates an efficient non-precious metal ORR catalyst, but also provides new ideas and experimental basis for the precise design of the next generation of single-atom catalysts through heteroatom axial coordination engineering.