Solid‐state storage of hydrogen molecules in carbon‐based light metal single‐atom materials is promising to achieve both high hydrogen storage capacity and uptake rate, but there is a lack of fundamental understanding and design principles to guide the rational design of the materials. Here, a theoretical relationship is established between the hydrogen capacity/rate and the structures of the heteroatom‐doped‐graphene‐supported light metal Li single atom materials for high‐efficient solid‐state hydrogen storage, which is verified by combining spectroscopic characterization, H2 adsorption/desorption measurements, and density functional theory (DFT) calculations. Based on the DFT calculations, a novel descriptor Φ is developed to correlate the inherent properties of dopants with the hydrogen storage properties, and further to screen out the best dual‐doped‐graphene‐supported light metal Li single‐atom hydrogen storage materials. The dual‐doped materials have a much higher hydrogen storage capability than the sole‐doped ones and exceed the best carbon‐based hydrogen storage materials so far. In this study, design principles and activity origin for the carbon‐based light metal single‐atom solid‐state hydrogen storage materials are elucidated. Additionally, a novel descriptor Φ is proposed to correlate the intrinsic properties of dopants with the hydrogen storage properties. The design principle and descriptor have the predictive ability to screen out the best dual‐doped‐graphene‐supported Li single‐atom hydrogen storage materials.