The oxygen reduction reaction (ORR) is a crucial process during hydrogen-based energy conversion at the cathode of proton-exchange membrane fuel cells, which causes a bottleneck owing to the high price and low efficiency of ORR catalysts. Single-atom catalysts (SACs) have garnered significant attention from researchers due to their exceptional activity and efficient atom utilization. To identify highly active SACs among numerous candidates, a three-step screening strategy was adopted to select the best ORR catalyst. Through this screening approach, the SIr@N8 SAC composed of S and Ir pair anchored N-doped graphene was identified to exhibit an excellent catalytic performance with an overpotential of 0.29 V. Its remarkable activity and stability make it a promising ORR catalyst. And the electronic structure analysis suggested that the electronic structure of active metal sites could be regulated by nonmetal coordinates to enhance the catalytic performance. This theoretical study is expected to provide an effective scanning strategy for identifying ORR catalysts with an outstanding catalytic performance.