<p>Direct methanol fuel cells are promising energy-supplying devices for future portable electronics, but the anodic methanol oxidation has been crying out for high-efficiency catalysts. Ruthenium oxide (RuO₂) exhibits the capacity to improve the catalytic performance of Pt-based materials, while the underlying mechanism is still not clear. Herein, we constructed carbon-encapsulated RuO₂ clusters supported Pt nanoparticles with enhanced catalytic activity and durability towards the methanol oxidation reaction (MOR), and the in-depth mechanism was studied by <i>in-situ</i> infrared absorption spectrum and first-principles computation. The carbon-encapsulated RuO₂ clusters alleviated the dissolution of metallic Ru in acidic media and regulated the electronic structure of Pt nanoparticles via the electronic metal-support interaction. <i>In-situ</i> attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) tracked the intermediates and confirmed the facilitated dissociation of interfacial water on the Pt-RuO₂/C at a low potential of 0.56 V, generating active OH species to promote the oxidative removal of CO intermediates and CO₂ generation. Theoretical calculations further confirmed the weakened CO adsorption energy on Pt-RuO₂ as well as the decreased reaction energy barrier of the rate-determining CO oxidation step. As a result, the Pt-RuO₂/C showed a MOR peak current density of 68.7 mA cm⁻², which was 1.7 and 2.9 times that of commercial PtRu/C and Pt/C catalysts. Besides, the current density of Pt-RuO₂/C reached 10.4 mA cm⁻² at 0.66 V, about 3.3 and 5.0 times that of commercial PtRu/C and Pt/C catalysts, indicating good catalytic activity at low potentials. The current work contributes some practical and theoretical basis to the development of a novel Pt-Ru electrocatalyst system for energy conversion techniques.</p>