In this paper, the hydrogen storage properties and reaction mechanism of the MgH2-Li3AlH6 composite system with the addition K2TiF6 were investigated for the first time. The temperature-programmed-desorption results show that the addition of 10 wt.% K2TiF6 to MgH2-Li3AlH6 composite system improves the onset desorption temperature to 120 degrees C and 225 degrees C for the first and second dehydrogenation stages, which is lowered by 60 degrees C and 45 degrees C, compared to un-doped composite. The re/dehydrogenation kinetics of MgH2-Li3AlH6 + 10 wt.% K2TiF6 were also improved significantly compared to un-doped composite. The Arrhenius plot demonstrated that the apparent activation energy of the MgH2-Li3AlH6 composite (150 kJ/mol) was reduced to 133 kJ/mol after the addition of 10 wt.% K2TiF6. The X-ray diffraction analysis shows the formation new phases of Al3Ti, LiF and TiH2 in the doped composite after the dehydrogenation and rehydrogenation processes that could act as the real catalyst in the MgH2-Li3AlH6 + 10 wt.% K2TiF6 composite which may promote the interaction between MgH2 and Li3AlH6, thus improving the hydrogen sorption properties. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.