AbstractPhotocatalytic oxygen evolution reaction (OER) by 2D semiconductors is a promising strategy for efficient energy conversion. The newly discovered 2D semiconductors MA₂Z₄ (M = transition metal, e.g., Mo, W; A = C, Si, and Ge; Z = N, P, and As) have shown characteristics of promising photocatalytic OER catalysts. Herein, an automated high‐throughput workflow is proposed to efficiently screen MA₂Z₄ photocatalytic OER catalysts, and further reveal the theoretical mechanism. The four criteria of semi‐conductivity, bandgap width/band edge position, structural stability, and free energy change, are proposed to screen MA₂Z₄ catalysts thermodynamically. The exciton properties and carrier mobility of these MA₂Z₄ are further studied to explore the high‐efficiency photocatalytic OER MA₂Z₄ with low exciton binding energy and high effective mass ratio. It is found that the bandgap width of MA₂Z₄ mainly depends on the strength of MZ bonding and the redistribution of electrons, while the catalytic effect is closely related to the adsorption capacity of O atom. In particular, β‐ZrSi₂N₄ and β‐HfSi₂N₄ are screened as efficient photocatalytic OER catalysts. This study develops a fully automated method and contributes to a complete framework for screening high‐efficiency photocatalytic OER catalysts.