Abstract: Developing low-cost, high-activity, and durable electrocatalysts for the hydrogen evolution reaction （HER） is crucial for sustainable hydrogen production. In this study, a cerium-doped nickel cobalt phosphide self-supported electrode （Ce-NiCoP/NF） was in-situ fabricated on nickel foam via a one-step electrodeposition method. Characterizations confirm that Ce was successfully incorporated into the NiCoP lattice and induces the formation of uniform and dense nanoarray architectures on the NF substrate. The resulting Ce-NiCoP/NF electrode exhibited remarkable HER performance in alkaline media （1 mol/L KOH）, achieving a current density of 10 mA·cm⁻²; at an overpotential of only 75 mV and maintaining stable operation for over 72 hours. Density functional theory （DFT） calculations elucidated the promotion mechanism of Ce doping, which manifests in three key aspects: enhancing H₂O adsorption, optimizing the thermodynamic landscape for water dissociation, and significantly lowering its energy barrier to accelerate HER kinetics. Additionally, Ce doping increased the density of states （DOS） near the Fermi level, promoting electron delocalization and improving both electrical conductivity and interfacial charge transfer. In summary, Ce doping simultaneously modulates reactant adsorption and electron transport to jointly boost catalytic performance. This rare-earth doping strategy delivers both experimental evidence and theoretical guidance for the design of high-performance non-noble electrocatalysts toward hydrogen evolution.