The microstructures of the rare-earth-based Low-Co AB5-type LaxMm1-x(NiMnSiAlFe)4.7Co0.2(x=0,1)alloys for hydrogen storage were determined by XRD and SEM,and the electrochemical performances of the as-cast and quenched alloys were measured synthetically.The effects of the substitution La for Mm on microstructures and electrochemical characteristics of the as-cast and quenched alloys were studied.The obtained results show that the substitution La for Mm extends the cycle life of the as-cast alloy and improves the discharge capacity of the alloys because the substitution La for Mm makes the secondary phase disappear and the cell volume enlarge.Rapid quenching can improve the cycle stability of the alloys,but it isn't notable to the as-quenched La1 alloy.It is mainly attributed to the larger grain produced by substitution La for Mm.