Hydrogen is regarded as an ideal substitute for fossil fuels on account of its advantages of high energy density, zero carbon emissions, and abundant reserves. Solid-state hydrogen storage is one of the most promising hydrogen storage methods in terms of high-volume storage density and safety. MgH2 is a promising solid hydrogen storage material because of its high hydrogen storage capacity and favorable cycle reversibility. Nevertheless, its inferior thermodynamic and kinetic properties restrict its extensive application. Catalyst modification is considered to be an efficient way to enhance the thermodynamic and kinetic properties of hydrogenation and dehydrogenation for MgH2. This review summarizes the latest research progress on MXene-based composites, such as MAX, single metal MXene, bimetallic MXene, MXene/elemental metal, and MXene/transition metal compounds for promoting the hydrogen storage performances of MgH2. At the same time, the catalyst of MXene-based composites to optimize the hydrogenation/dehydrogenation kinetics, long cycle performance and catalytic mechanism of Mg/MgH2 are discussed in detail.