A brief review of state-of-the art advances in improving performances of the lightweight complex hydrides LiMg-N-H system is reported. Among the hydrogen storage materials, Li-Mg-N-H combination systems are regarded as one of the most potential candidates for the vehicular applications owing to their high hydrogen storage capacity( > 5 wt% H) and a more appropriate thermodynamic properties of hydrogen absorption and desorption. In the Li-Mg-N-H systems, tremendous efforts have been devoted to improving the hydrogen storage properties by adjusting composition, revealing reaction mechanisms, adding catalysts and refining the microstructures, etc. During the studies, different mechanisms, such as the coordinated two-molecule or multimolecule reaction mechanism and the ammonia-mediated mechanism, are proposed and applied under some certain conditions. Catalysis and nanosizing are very effective in enhancing the kinetic properties and thermodynamic destabilization of Li-Mg-N-H systems. Due to nano effects, the space-confinement and nanoconfinement seems to be more effective for improving the hydrogen storage performance, and it is great significant to develop hydrogen storage materials by studying the nanoconfined effects on the Li-Mg-N-H systems. A brief review of state-of-the-art advances in improving performances of the lightweight complex hydrides LiMg-NH system is reported. Among the hydrogen storage materials, Li-Mg-NH combination systems are one as the most potential candidates for the vehicular applications owing to their high hydrogen storage capacity (> 5 wt% H) and a more appropriate thermodynamic properties of hydrogen absorption and desorption. In the Li-Mg-NH systems, tremendous efforts have been devoted to improving the hydrogen storage properties by adjusting composition, revealing reaction mechanisms, adding catalysts and refining the microstructures, etc. during the studies, different mechanisms, such as the coordinated two-molecule or multimolecule reaction mechanism and the ammonia-mediated mechanism, are proposed and applied under some certain conditions. Catalysis and nanosizing are very effective in enhancing the kinetic properties and thermodynamic destabilization of Li-Mg-NH systems. Due to nano effects, the space-confinement and nanoconfinement seems to be more effective for improving the hydrogen storage performance, and it is great significant to develop hydrogen storage materials by studying the nanoconfined effects on the Li-Mg-N-H systems.