The rational design of Cu-based catalysts with tailored interfacial structures and electronic states remains challenging yet essential for advancing hydrogen production via methanol steam reforming (MSR). Here, we developed a samarium-mediated strategy to construct a 30Sm-CuAl catalyst. The introduction of Sm promotes Cu dispersion and induces strong metal-support interactions, resulting in the formation of Sm 2 O 3 -encapsulated Cu nanoparticles enriched with Cu + -O-Sm interfaces. The optimized 30Sm-CuAl demonstrates exceptional MSR performance, achieving a hydrogen production rate of 1,126 mmol g cat −1 h −1 at 250°C. Mechanistic studies revealed that the reaction follows the formate pathway in x Sm-CuAl, with formate accumulation identified as the primary reason for the deactivation of 30Sm-CuAl. Dynamic regeneration of 30Sm-CuAl through redox treatment restores its activity, thereby enabling cyclic operation. These findings provide insights into rare-earth oxide regulation of Cu-based catalysts and lay the foundation for targeted resolution of formate intermediate accumulation to enhance MSR stability.