The effect of dielectric barrier discharge plasma-assisted milling (P-milling) on the hydrogen generation properties of Mg-graphite composites is investigated in this work. The results show that P-milling of Mg and 20 wt.% expanded graphite (EG) can significantly enhance the hydrolysis properties of Mg, and the obtained composite may generate 614.3 mL g H with a hydrolysis conversion rate of 83.5% in 25 min. P-milling shows the optimal effect on the hydrolysis of Mg-graphite composites by comparing the varied milling process. The apparent activation energy of hydrolysis in deionized water of the Mg-EG composite obtained by P-milling is determined to be 67.6 kJ mol . The hydrolysis mechanism of this Mg-EG composite is also discussed. Scaled hydrogen supply test of 10 g of the Mg-EG composite by P-milling is demonstrated on a hydrogen generator and it shows a maximum hydrogen flow rate of 12.3 L min with a conversion rate of 93.9%. The findings here present that the P-milled Mg-EG composite with high hydrogen density and low cost can be a promising hydrogen generation material.