This study presents a novel approach to optimize acidic oxygen evolution electrocatalysis by precisely regulating the Ru-O covalency in RuOx through the introduction of lanthanide elements. The research demonstrates that lanthanide elements, with their 4f orbitals shielded by 5s/5p orbitals, can effectively modulate Ru-O covalency, leading to enhanced stability and catalytic performance. Theoretical calculations and experimental results show that Er-RuOx is the optimal catalyst, exhibiting a stability 35.5 times higher than RuO2. The Er-RuOx-based device requires only 1.837 V to reach 3 A cm⁻² and maintains long-term stability at 500 mA cm⁻² for 100 h with a degradation rate of 37 μV h⁻¹. The study highlights the importance of controlling Ru-O covalency for efficient and durable oxygen evolution reactions, offering a promising strategy for the development of cost-effective and sustainable electrocatalysts for green hydrogen production. The findings provide a fundamental framework for precise Ru-O covalency control, guiding the design of ruthenium-based catalysts suitable for practical implementation in proton exchange membrane water electrolysis systems.This study presents a novel approach to optimize acidic oxygen evolution electrocatalysis by precisely regulating the Ru-O covalency in RuOx through the introduction of lanthanide elements. The research demonstrates that lanthanide elements, with their 4f orbitals shielded by 5s/5p orbitals, can effectively modulate Ru-O covalency, leading to enhanced stability and catalytic performance. Theoretical calculations and experimental results show that Er-RuOx is the optimal catalyst, exhibiting a stability 35.5 times higher than RuO2. The Er-RuOx-based device requires only 1.837 V to reach 3 A cm⁻² and maintains long-term stability at 500 mA cm⁻² for 100 h with a degradation rate of 37 μV h⁻¹. The study highlights the importance of controlling Ru-O covalency for efficient and durable oxygen evolution reactions, offering a promising strategy for the development of cost-effective and sustainable electrocatalysts for green hydrogen production. The findings provide a fundamental framework for precise Ru-O covalency control, guiding the design of ruthenium-based catalysts suitable for practical implementation in proton exchange membrane water electrolysis systems.