In this paper, the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10 - x wt％ CeO2 (x = 0, 4, 8) alloys were prepared successfully by vacuum induction smelting and ball milling. The microstructure, hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail. The results show that the Mg85Cu5Ni10 alloys with CeO2 additive have faster hydrogenation/dehydro-genation kinetics and better thermodynamic properties. The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt％ CeO2. CeO2 contributes to producing structural defects, nanocrystallines, grain boundaries, partial amorphous, lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process. Mean-while, CeO2 additive weakens the bond energy of Mg-H. These microstructural changes caused by CeO2 additive improve the hydrogen storage performance of Mg85Cu5Ni10 markedly.