Conventional powdery RuO₂ anodes for proton exchange membrane water electrolyzer (PEMWE) suffer from sluggish interfacial charge transport and severe structural degradation. We propose porous graphdiyne (GDY) as a multifunctional coating on the self-supporting RuO₂-based electrode, creating a GDY@RuO₂ heterostructure to address the above interfacial issues and activity–stability trade-offs. Simulations study reveals that GDY induces interfacial directional charge transfer through sp-C–Ru bonds, modifying electronic structure, impeding O/Ru vacancy formation, and shifting oxygen evolution reaction (OER) pathway to the adsorbate evolution mechanism (AEM). Guided by these, RuO_2−x nanoparticles were deposited on titanium mesh, followed by controlled in-situ GDY growth. The optimized medium-thickness coating (GDY_M@RuO_2−x) exhibits exceptional performance: an overpotential of 196 mV at 10 mA·cm⁻² in 0.5 M H₂SO₄, negligible voltage decay (0.046 mV·h⁻¹) over 500 h operation, and a remarkable stability number (S-number). Due to the improved interfacial Ohmic and charge transfer resistance between electrode-plate/PEM, the PEMWE using GDY armored anode can achieve 1 A·cm⁻² at 1.55 V and stable operation at 0.5 A·cm⁻² for 500 h (0.17 mV·h⁻¹). Comprehensive analyses confirm the GDY efficacy of robust physical protection and its dynamic electron replenishment, optimizing Ru/O electronic structure to direct OER following AEM, reinforcing the RuO_2−x structure integrity.