Tuning the metal-support interaction of supported metal catalysts has been found to be the most effective approach to modulating electronic structure and improving catalytic performance. But practical understanding of the charge transfer mechanism at the electronic level of catalysis process has remained elusive. Here, it is reported that ruthenium (Ru) nanoparticles can self-accommodate into Fe O and carbon support (Ru-Fe O /C) through the electronic metal-support interaction, resulting in robust catalytic activity toward the alkaline hydrogen evolution reaction (HER). Spectroscopic evidence and theoretical calculations demonstrate that electronic perturbation occurred in the Ru-Fe O /C, and that charge redistribution directly influenced adsorption behavior during the catalytic process. The RuO bond formed by orbital mixing changes the charge state of the surface Ru site, enabling more electrons to flow to H intermediates (H ) for favorable adsorption. The weak binding strength of the RuO bond also reinforces the anti-bonding character of H* with a more favorable recombination of H* species into H molecules. Because of this satisfactory catalytic mechanism, the Ru-Fe O /C supported nanoparticle catalyst demonstrated better HER activity and robust stability than the benchmark commercial Pt/C benchmark in alkaline media.