Coordination engineering strategy for optimizing the catalytic performance of single-atom catalysts (SACs) has been rapidly developed over the last decade. However, previous reports on copper SACs for nitrate reduction reactions (NO₃RR) have mostly focused on symmetric coordination configurations such as Cu-N₄ and Cu-N₃. In addition, the mechanism in terms of the regulation of coordination environment and catalytic properties of SACs has not been well demonstrated. Herein, we disrupted the local symmetric structure of copper atoms by introducing unsaturated heteroatomic coordination of Cu−O and Cu−N to achieve the coordination desymmetrization of Cu-N₁O₂ SACs. The Cu-N₁O₂ SACs exhibit an efficient nitrate-to-ammonia conversion with a high FE of ~96.5 % and a yield rate of 3120 μg NH₃ h⁻¹ cm⁻² at −0.60 V vs RHE. As indicated by in situ Raman spectra, the catalysts facilitate the accumulation of NO₃⁻ and the selective adsorption of *NO₂, which were further confirmed by the theoretical study of surface dipole moment and orbital hybridization. Our work illustrated the correlation between the coordination desymmetrization and the catalytic performance of copper SACs for NO₃RR.