For improving electrochemical performances of Mg-Ni-based alloys at ambient temperature, a portion of Mg was succeeded by Ce and the surface modification treatment was conducted by mechanical coating Ni. The nanocrystalline and amorphous Mg1-xCexNi0.9Al0.1 (x = 0, 0.02, 0.04, 0.06, 0.08) + 50 wt%Ni metals were prepared. Impacts of Ce content and milling duration on the structure and electrochemical hydrogen storage properties have been researched. The results exposed that, the as-milled alloys can absorbing/desorbing hydrogen electrochemically very well at ambient temperature. Activation is not necessary as the first cycle can reach the maximal discharge capacity. Through 5 and 20 h milling, the maximum discharge capacities of alloys are 378.8 and 545.3 mAh/g, respectively. Cycling stability improves with Ce content and milling time growing. Specifically speaking, the retention rate of capacity at 100th cycle (S-100 = C-100/C-max) ascends from 36% to 66% for 5 h milled alloy and from 48% to 76% for 20 h milled alloy with Ce content growing from 0 to 0.08. Furthermore, many indexes such as electrochemical impedance spectrum, potentiodynamic polarization curves, high rate discharge ability, potential-step measurements, etc. proved that varying Ce content makes the alloys get their best electrochemical kinetic property.