In this work, we developed Ni nanoparticles (NPs) encapsulated in a highly ordered MIL-101 as catalysts for CO₂ methanation by double solvent method (DSM) and multiple impregnation method (IM). The 20Ni@MIL-101(DSM) catalyst exhibited unexpectedly higher activity (CH₄ TOF was 1.63 x 10^-3 s^-1 at 300 ℃), thermal stability and lower activation energy (88.01 kJ/mol) for CO₂ methanation than the 20Ni@MIL-101(IM) catalyst. Based on activity results and characterization studies using XRD, H₂-TPR, BET, TEM, XPS, FT-IR and TGA techniques, the small-sized high dispersion Ni NPs in the frameworks of 20Ni@MIL-101(DSM) exposed Ni(1 1 1) facet are main active species. The results of density-functional theory (DFT) calculations indicated that the potential energy barrier was about 10.0 kcal/mol for CO₂ dissociation into CO_ads and O_ads over the Ni(1 1 1) surface, which was lower than Ni(2 0 0) plane (20.3 kcal/mol). These results uncover the dependence of the activation energy of the CO₂ methanation on the Ni plane over Ni-based catalysts. These understandings will probably be applicable in the development of highly efficient CO₂ methanation catalysts at low temperature region.