Structural change and dehydriding mechanism of MgH2 with atomic Fe incorporation from reactive ball milling are characterized and simulated by first-principles calculation. Two kinds of hydrides beta- and gamma-MgH2 are formed from Mg powders under hydrogen atmosphere by 3.0 h of milling with pretreated anthracite as milling aid. Experimental studies suggest that the atomic Fe can be incorporated onto MgH2 surface by the shearing effect of Fe-based milling balls on Mg/MgH2 particles. The incorporated Fe has a high dispersity on MgH2 surface and can form atomic clusters FeH4/FeH2 by combining with H anions. The dehydriding reaction of the Fe-incorporated MgH2 begins at hydride surface and shows an enhanced performance with apparent activation energy of 110.3 kJ mol(-1). Theoretical studies suggest that the incorporated Fe can act as a bridge that contributes to electron transfer from H anion to Mg cation before H-2 molecule formation. The intrinsic reason of atomic Fe in catalyzing dehydriding reaction of MgH2 lies in its moderate strength of electron attraction. (C) 2016 Elsevier B.V. All rights reserved.