Abstract: The development of efficient and robust oxygen non-precious catalysts for the oxygen evolution reaction (OER) remains a critical scientific hurdle in realizing cost-effective renewable energy conversion systems. Herein, we present a rapid laser irradiation synthesis strategy for the successful fabrication of sub-10 nm FeCoNiMnCr high-entropy alloy nanoparticles (HEA-NPs) on multi-wall carbon nanotube (MWCNT) paper, serving as highly efficient OER electrocatalysts. The synthesis of high-entropy alloy nanoparticles with precise control was accomplished through systematic optimization of laser processing parameters. Structural characterization via X-ray diffraction, high-resolution transmission electron microscopy, and high-angle annular dark-field scanning transmission electron microscopy collectively verified the formation of a phase-pure face-centered cubic crystal structure with homogeneous elemental mixing at the atomic scale. Furthermore, COMSOL Multiphysics simulations confirm that this rapid and discontinuous laser irradiation approach enables the precursor material to undergo ultrafast heating and quenching processes, effectively suppressing Ostwald ripening phenomena, which is conducive to the formation of ultrafine (sub-10 nm) high-entropy alloy nanoparticles. The synthesized HEA-NPs catalyst demonstrates exceptional oxygen evolution activity in alkaline electrolyte (1 M KOH), achieving a current density of 10 mA·cm⁻² at a low overpotential of 255 mV while maintaining remarkable stability with negligible activity decay during prolonged operation (>100 h), representing state-of-the-art performance among non-precious metal catalysts. This study provides perspectives on the rapid preparation and performance regulation of HEA-NPs catalysts.