Efficient electroreduction of CO₂ into CO and other chemicals turns greenhouse gases into fuels and value-added chemicals, holding great promise for a closed carbon cycle and the alleviation of climate changes. However, there are still challenges in the large-scale application of CO₂ electroreduction due to the sluggish kinetics. Herein we develop a self-assembly strategy to synthesize a highly efficient CO₂ reduction electrocatalyst with atomically dispersed Ni-N₄ active centers anchored on polymer-derived mesh-like N-doped carbon nanofibers (Ni-N₄/NC). The Ni-N₄/NC exhibits high selectivity for CO₂ reduction reaction with CO Faradaic efficiency (CO FE) above 90% over a wide potential range from −0.6 to −1.0 V vs. RHE. The catalyst reaches a maximum CO FE up to 98.4% at −0.8 V with a TOF of 1.28 x 10⁵ h^–1 and Tafel slope of 113 mV·dec^–1. The catalyst also exhibits remarkable stability, with little change in current density and CO FE over a 10-hour durability test at –0.8 V vs. RHE. This method provides a new route for the synthesis of highly efficient CO₂ reduction electrocatalyst.