Multifunctional single atomic catalysts (SACs) are advantageous for the co-reduction of NOx mixtures. In this work, we used a strategy for high-throughput screening of SACs of NOxRR based on density functional theory. SACs were designed based on the B and N defects of hexagonal BN, and its hydrogenation in NOxRR was studied. The stability of SACs is found to be regulated by the spatial radius of the metal atoms and the electronic structure of the surface. Electron enrichment in the metal center facilitates activation of the intermediate *NHO and reduces the limiting potential. The activity of SACs can be briefly described by ΔG*NO. Ultimately, Mn-BN-B is identified as a SAC with excellent performance for NO3RR, NO2RR and NORR, because of the limiting potential of − 0.26 V, and Cu, Co-BN-B also showed good NORR activity. Our work provides a procedure for efficiently screening multifunctional electrocatalysts to simultaneously reduce all NOx species to synthesize NH3.