Crystal structure, electronic structure and bonding characteristics of LaNi5-xCox(x=0, 0.5) and its hydride were investigated by the density functional theory based on general gradient approximation (GGA) and the ultra-soft plane-wave pseudopotential method. The total energy, energy band structure, density of states and Mulliken population were obtained. The results show that the interaction between Ni2c and La atoms is larger than that between Ni3g and La atoms in LaNi5 alloy. There is obvious covalent interaction between Ni2c―Ni2c and Ni3g―Ni3g. However, the covalent interaction is reduced after introduction of Co and H atoms. The interaction between H and Ni3g atoms is larger than that between H and Ni2c atoms. The expansion along a axis is larger than that along c axis because the lattice expansion results in outward moving of Ni2c atoms after hydrogen atom enters the tetrahedron