We exploited a hydrogen-passivated germanium atomic cluster(Ge_(10)H_(16) as a model to study the mechanism of lithium alloying with germanium. Based on the density functional theory, the electronic and crystal structures of lithium-alloyed Ge_(10)H_(16 were investigated. The theoretical results indicate that the alloying of lithium with Ge_(10)H_(16 will weaken the germanium-hydrogen bond and repel the closest germanium atom away from the alloyed lithium atom. Based on the maps of the electron density distribution, the nature of the lithium-germanium chemical bond was analyzed. Moreover, the diffusion process of the lithium on the Ge_(10)H_(16 cluster was detected, which suggested that there is a close relationship between the diffusion barriers and the coordination number around the lithium atom. We exploited a hydrogen-passivated germanium atomic cluster (Ge_ (10) H_ (16) as a model to study the mechanism of lithium alloying with germanium. Based on the density functional theory, the electronic and crystal structures of lithium-alloyed Ge_ (10) The theoretical results indicate that alloying of lithium with Ge_ (10) H_ (16 will weaken the germanium-hydrogen bond and repel the closest germanium atom away from the alloyed lithium atom. Based on the maps of the electron density distribution, the nature of the lithium-germanium chemical bond was analyzed. Furthermore, the diffusion process of the lithium on the lithium on the ge_ (10) H_ (16 cluster was detected, which suggested that there is a close relationship between the diffusion barriers and the coordination number around the lithium atom.