The bulk Mg-M (M = Nickel [Ni], cerium [Ce], and Lanthanum [La]) alloys are successfully ameliorated by high-energy ball milling (HEBM) to modify the hydrolysis H 2 generation performance in simulated seawater solution (3.5 wt% NaCl). The H 2 generation kinetics, rate-limiting steps, thermodynamics and the hydrolysis mechanism are investigated by combining the fitting results of the hydrolysis curves and microstructures information. The results indicate that the as-cast Mg25Ni possesses higher generation capacity and faster initial rate. The capacities of as-cast Mg25Ni, Mg30Ce, and Mg30La alloys at 48 C within 180 minutes are 760 mL g −1 , 725 mL g −1 , and 525 mL g −1. The hydrolysis H 2 generation apparent activation energies of the as-cast Mg25Ni, Mg30Ce, and Mg30La alloys are 30.92, 17.05, and 28.04 kJÁmol −1 , respectively. The HEBM technique can elevate the hydrolysis performance of Mg-M alloys. And the highest H 2 producing capacity as high as 589 mL g −1 is obtained by HEBM Mg30La alloy at 48 C within 30 minutes. The hydrolysis apparent activation energies E a are 9.57, 14.65, and 23.88 kJ/mol for HEBM Mg25Ni, Mg30Ce, and Mg30La alloys. The initial rate and the final yield of H 2 generation for Mgbased alloys are affected by the activity of matrix alloy, microstructure, particle size, surface state, and many other factors. K E Y W O R D S H 2 production, HEBM, hydrogen generation mechanism, kinetics, Mg intermediate alloys 1 | INTRODUCTION Hydrogen is currently the most appealing option for fossil fuels in the future. The production of H 2 is the primary problem of hydrogen utilization. 1-5 The hydrogen-energy process chain is consisted by the hydrogen production 6 , hydrogen storage 7-10 and regeneration. 11-13 Nowadays, the wide usages of H 2 energy are still seriously prevented