Nanocrystalline and amorphous La_(2–x)Sm_xMg_(16)Ni+200wt.% Ni(x=0, 0.1, 0.2, 0.3, 0.4) alloys were prepared by mechanical milling technology. The structures of as-cast and milled alloys were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). Electrochemical performance of the alloy was studied by using an automatic galvanostatic system. The electrochemical impedance spectra(EIS) and Tafel polarization curves were measured by electrochemical workstation. The results indicated that the structures of the as-cast and milled alloys presented a multiphase structure with nanocrystalline and amorphous phase, moreover, transforming from nanocrystalline to amorphous phase with Sm doping. With the increase of Sm content, the maximum discharge capacity of the alloy was decreased from 922.6 to 649.1 m Ah/g, the high-rate discharge ability(HRD) was decreased, the cycle stability was strengthened, and the alloy exhibited excellent electrochemical kinetics. In addition, the charge-transfer resistance(R_(ct)) of alloy was lessened from 0.05874 to 0.02953 ? and the limiting current density(I_L) was descended from 2.08366 to 1.04592 A/g with increasing Sm content. The structures of as-cast and milled alloys were (La) (2-x) Sm_xMg_ (16) Ni + 200wt.% Ni investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of the alloy was studied by using an automatic galvanostatic system. The electrochemical impedance spectra (EIS) and Tafel polarization curves were measured by electrochemical workstation. The results indicated that the structures of the as-cast and milled alloys presented a multiphase structure with nanocrystalline and amorphous phase, moreover, transforming from nanocrystalline to amorphous phase with Sm doping. With the increase of Sm content, the maximum discharge capacity of the alloy was decreased from 922.6 to 649.1 m Ah / g, the high-rate discharge ability (HRD) was decreased, the cycle stability was strengthened, and the alloy exhibit excellent e In addition, the charge-transfer resistance (R_ (ct)) of alloy was lessened from 0.05874 to 0.02953 and the limiting current density (I_L) was descended from 2.08366 to 1.04592 A / g with increasing Sm content.