Degradation behaviors of three typical La-Mg-Ni alloys, La 2 MgNi 9 , La 1.5 Mg 0.5 Ni 7 and La 4 MgNi 19 , were studied. La 1.5-Mg 0.5 Ni 7 with (La,Mg) 2 Ni 7 as main phase presents better discharge capacity and cycling stability. The three alloys suffer severe pulverization and corrosion after electrochemical cycles, which are considered to be the significant factor attributing to the capacity deterioration. However, the overall corrosion extent of the three cycled alloys aggravates successively, which is inconsistent with the result that La 2 MgNi 9 presented poor cycling stability and also the assumption that alloy with high Mg content is easy to be corroded. The intrinsic anti-corrosion and anti-pulverization characteristics of the three alloys are mainly focused in this work. Immersion corrosion experiments demonstrate that the Mg-rich phases are more easily to be corroded. The corrosion resistance of the three alloys presents an improved trend which is inversely proportional to abundance of the Mg-rich phases. However, the anti-pulverization abilities present an inverse trend, which is closely related to the mechanical property of various phase structures. LaNi 5 with the highest hardness is easy to crack, but the soft (La,Mg)Ni 2 is more resistant to crack formation and spreading. Thus, the weaker corrosion of La 2 MgNi 9 after electrochemical cycling is attributed to the better intrinsic anti-pulverization capability though the anti-corrosion is poor. As La 4 MgNi 19 possesses excellent corrosion resistance, enhancement of the anti-pulverization ability is urgent for improvement in the cycling stability.