We describe the synthesis of MgH2 using autocatalytic effect of MgH2. The MgH2 was synthesized by ball milling Mg with 5 wt% of MgH2. The ball milling was carried out at different pressures of 15, 30 and 45 atm of H-2 followed by heat treatment (heating under vacuum and annealing at 30 atm of H-2 pressure (at 350 degrees C) for 10 h). It has been found that the MgH2 synthesized using 30 atm of H-2 pressure during ball milling, followed by heat treatment and annealing (MgH(2)30BM) is the optimum material as it has lowest desorption temperature (325 C) faster rehydrogenation kinetic (6.60 wt% within 30 min at 300 degrees C and 20 atm hydrogen pressure). Also MgH(2)30BM maintains the storage capacity of more than 6.00 wt% (loss of 0.6 wt%) after 10 cycles of de/re-hydrogenation. The as synthesized MgH2 has superior de/re-hydrogenation properties and is-4 times cheaper as compared to MgH2 procured from the chemical company like Alfa-Aesar. It is to be mentioned that under above mentioned temperature and pressure conditions the stand alone Mg (without having MgH2 as catalyst) doesnot at all converts to MgH2. The present study opens the gateway for economical synthesis of MgH2 at large scale. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.