The Ni-coated carbon nanotubes (Ni@CNT) composite was synthesized by the facile “filtration + calcination” of Ni-based metal-organic framework (MOF) precursor and the obtained composite was used as a catalyst for MgH₂. MgH₂ was mixed evenly with different amounts of Ni@CNT (2.5, 5.0 and 7.5, wt.%) through ball milling. The MgH₂-5wt.%Ni@CNT can absorb 5.2 wt.% H₂ at 423 K in 200 s and release about 3.75 wt.% H₂ at 573 K in 1000 s. And its dehydrogenation and rehydrogenation activation energies are reduced to 87.63 and 45.28 kJ/mol (H₂). The in-situ generated Mg₂Ni/Mg₂NiH₄ exhibits a good catalytic effect due to the provided more diffusion channels that can be used as “hydrogen pump”. And the presence of carbon nanotubes improves the properties of MgH₂ to some extent.