Abstract: The invention concerns a method for preparing a nanocomposite based on magnesium and another element or compound known to absorb hydrogen and hardly miscible when ground with magnesium or its hydride, such as vanadium, titanium or niobium. The method is characterised in that it consists in submitting magnesium or a compound based on magnesium known to absorb hydrogen to hydrogenation to obtain the corresponding hydride in powder form. Said resulting powder hydride is then mixed with the other element or compound or a hydride of said other element or compound and the resulting mixture is subjected to intense mechanical grinding until the corresponding nanocomposite is obtained in the form of a hydride. Finally, if necessary, the resulting nanocomposite is subjected to hydrogen desorption.