<p>Electrocatalytic CO₂ reduction reaction (CO₂RR) to high-value-added products is a crucial approach for promoting carbon recycling and mitigating energy challenges. Here, extensive theoretical screenings were conducted on the nitrogen-doped graphene-supported heteronuclear dual-atom catalysts (DACs) M₁/M₂-NC (M = V, Cr, Mn, Fe, Co, Ni, and Cu) for CO₂RR using density functional theory (DFT) calculations. The calculations indicate that Mn/Cu-NC exhibits superior catalytic activity and selectivity for the CO₂RR to HCOOH with a limiting potential as low as −0.15 V. The superior performance is attributed to the strong <i>d</i>-electron coupling between Mn and Cu dual atoms in Mn/Cu-NC, which results in an upward shift of the <i>d</i>-band center of the Mn single atom closer to the Fermi level. Moreover, the adsorption of the key intermediate *OCHO on the Mn single atom was further enhanced, thereby reducing the limiting potential and improving the catalytic performance for CO₂RR. This work offers a comprehensive theoretical insight into the catalytic mechanism of the novel Mn/Cu-NC DAC for CO₂RR and establishes a critical descriptor of <i>d</i>-band center of the catalytic active center to determine the catalytic activity of DACs for CO₂RR, thereby providing guidance for the future design and fabrication of graphene-based metal DACs for CO₂RR.</p>