The Mg2Ni-1.0%Pd(mass fraction)alloy power was prepared by mechanical alloying.XRD and AFM analysis were used to identify the phase and microstructure of the powder milled for 20 h.The P-C-T curves and kinetics curves of Mg2Ni-1.0%Pd-H2/D2 system were measured.The results show that the particle size of Mg2Ni-1.0%Pd alloy powder prepared by mechanical alloying was between 10 nm~50 nm.Compared with the Mg2Ni alloy prepared by melting,the enthalpy of nanocrystalline Mg2Ni-1.0%Pd alloy decreased upon hydrogen absorption and increased upon hydrogen desorption.The alloy had a reversible storage capacity as high as 1.06(H/M,atom ratio).Compared with absorbing-desorbing H2,the plateaus pressure under the same temperature increased and the enthalpy decreased on the P-C-T curves of the alloy absorbing-desorbing D2.The isotope effects in nanocrystalline Mg2Ni-1.0%Pd-H2 and D2 interaction were noticeable.The rate curves of absorbing H2 and D2 were measured at different temperatures,and the relationship of the rate and temperature changed around 573 K.