In order to improve the electrochemical properties of hydrogen storage alloys Mg2Ni, the modified alloy Mg_1.8 Zr_0.2Ni and MgTi₃ was prepared respectively by mechanical alloying (Mechanical Alloying, MA). Then the amorphous modified alloy Mg1.8Zr0.2Ni- (1.2-x) Ni -xMgTi₃ was prepared by ball milling a certain percentage Mg_1.8 Zr_0.2Ni, MgTi₃ and Ni. The results show that the composite hydrogen storage alloys after partially replace modified and coating modified have a large number of nanoscale folds, layered voids and multiphase structural defects in their the surface and the interior. With the increase of MgTi₃ content, the initial discharge specific capacity of Mg_1.8Zr_0.2Ni- (1.2-x) Ni -xMgTi₃ is also gradually increased. When the content of MgTi₃ was x=0.5, the initial discharge specific capacity was 973.3 mAh.g_-1. But when the content of MgTi₃ was more than x=0.5, the initial discharge specific capacity decreased rapidly. The study shows that the addition of MgTi₃ is not beneficial to the cycle stability and high rate discharge performance of the composite hydrogen storage alloys. By tested to the linear polarization,anodic polarization and exchange impedance of Mg_1.8Zr_0.2Ni- (1.2-x) Ni -xMgTi₃, the electrochemical reaction of surface, charge transfer process, the hydrogen diffusion in the alloy and the performance of their electrochemical kinetics of modified alloys were further researched.