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The phase structure and hydrogen storage properties of LaMg3.70Ni1.18 alloy were investigated.The LaMg3.70Ni1.19 alloy consists of main LaMg2Ni phase,minor La2Mg17 and LaMg3 phases.The alloy can be activated in the first hydriding/dehydriding process,and initial LaMg2Ni,La2Mg17,and LaMg3 phases transfer to LaH2.34,Mg,and Mg2Ni phases after activation.The reversible hydrogen storage capacity of the LaMg3.70Ni1.18 alloy is 2.47 wt.％ at 558 K,which is higher than that of the LaMg2Ni alloy.The pressure-composition-temperature (PCT) curves display two hydriding plateaus,corresponding to the formation of MgH2 and Mg2NiH4.However,only one dehydriding plateau is observed,owing to the synergetic effect of hydrogen desorption between MgH2 and Mg2NiH4.The uptake time for hydrogen content to reach 99％ of saturated state is less than 250 s,and 90％ hydrogen can be released in 1200 s in the experimental conditions,showing fast kinetics in hydriding and dehydriding.The activation energies of the LaMg3.70Ni1.18 alloy are -51.5 ± 1.1 kJ/mol and -57.0 ± 0.6 kJ/mol for hydriding and dehydriding,respectively.The hydriding/dehydriding kinetics of the LaMg3.70Ni1.18 alloy is better than that of the Mg2Ni alloy,owing to the lower activation energy values.