A kind composite of MgH2-In was prepared by ball milling the powder mixtures of MgH2 and In on a planetary mill. XRD was used to analyze the phases and phase transition during hydriding/dehydriding process of the composite. The dehydriding properties and phase transition temperature of the composite were investigated by DSC and GC (Gas Chromatograph). The thermodynamic and kinetic properties of hydrogenation/dehydrogenation of the composite were measured by the automatic gas adsorption instrument based on Sievert principle. The results indicate that the enthalpy and activation energy of hydrogen desorption of MgH2 are significantly reduced due to the formation of Mg3In and Mg(In) solid solution during the dehydriding process. Thus the dehydriding temperature of MgH2 is decreased, and the kinetics is greatly improved