This review article focuses on the structural engineering of atomic catalysts for electrocatalysis, particularly single-atom catalysts (SACs), diatomic catalysts (DACs), and triatomic catalysts (TACs). The geometric and electronic structures of metal active centers are crucial for achieving high-efficiency catalytic activity and selectivity. The article systematically introduces how these structures influence catalytic performance, including the role of substrates, central metal atoms, and coordination environments. It also discusses theoretical understandings such as synergistic effects, defect-coupled spin state changes, and crystal field distortion spin state changes. Challenges in optimizing atomic catalysts for electrocatalysis applications, such as controlled synthesis, increasing active site density, enhancing intrinsic activity, and improving stability, are highlighted. The review further examines the structure-function relationships of atomic catalysts in various electrocatalytic reactions, including CO2 reduction, nitrogen reduction, oxygen reduction, hydrogen evolution, and oxygen evolution. Finally, it proposes technical challenges and research directions to guide the development of high-performance atomic catalysts.This review article focuses on the structural engineering of atomic catalysts for electrocatalysis, particularly single-atom catalysts (SACs), diatomic catalysts (DACs), and triatomic catalysts (TACs). The geometric and electronic structures of metal active centers are crucial for achieving high-efficiency catalytic activity and selectivity. The article systematically introduces how these structures influence catalytic performance, including the role of substrates, central metal atoms, and coordination environments. It also discusses theoretical understandings such as synergistic effects, defect-coupled spin state changes, and crystal field distortion spin state changes. Challenges in optimizing atomic catalysts for electrocatalysis applications, such as controlled synthesis, increasing active site density, enhancing intrinsic activity, and improving stability, are highlighted. The review further examines the structure-function relationships of atomic catalysts in various electrocatalytic reactions, including CO2 reduction, nitrogen reduction, oxygen reduction, hydrogen evolution, and oxygen evolution. Finally, it proposes technical challenges and research directions to guide the development of high-performance atomic catalysts.