Traditional steam methane reforming (SMR) catalysts face significant challenges, particularly irreversible deactivation caused by sintering-induced aggregation of active components. A series of hierarchical porous carbon (HPC)-based catalysts with different Ni/Mg molar ratios were prepared to address this problem. The HPC support facilitated SMR reactions through a dual-anchoring catalytic mechanism, combining physical confinement by the hierarchical porous structure and chemical anchoring via oxygen-containing functional groups. Among these catalysts, the active components were present as NiO–MgO solid solutions, which enhanced the dispersion of active species and strengthened the interaction between the support and active components. The synergistic effect between the HPC support and NiO–MgO solid solutions collectively improved catalytic activity and long-term operational stability. Notably, the 1Ni–1Mg/HPC catalyst demonstrated optimal performance, with CH₄ conversion increasing from 38.15% to 88.11% for the Ni/HPC catalyst at 650 °C, while the H₂ yield reached 68.33%, and the catalyst showed negligible activity decay during 80 h of continuous operation. These results indicated that a highly active and stable SMR catalyst had been developed.