Atomically dispersed catalytic metal sites anchored on N-doped carbon support catalysts (M-N-C) show great prospects for CO₂ electroreduction. Here, single-layer NiZn layered double hydroxides (NiZn-LDHs) was used as a sacrificial assistant to fabricate single-Ni atom anchored on ultrathin porous carbon catalyst. NiZn-LDHs were exfoliated to single-layer by polyhydroxy compounds which took as the carbon resource in Ni-N-C, and single layer NiZn LDHs taking as the Ni resource could avoid the agglomeration of Ni atoms during calcining. The CO Faradaic efficiency (FE_CO) of the synthesized Ni-N-C catalyst exceeded 90% at −0.6 to −1.0 V and a FE_CO of 95.2% with a current density of 24 mA cm⁻² at −0.9 V. This work not only provides a new method for preparing M-N-C catalysts, but also offers an effective and controllable strategy for large-scale production of high-performance single-atom catalysts.