After the crystal structure of LaNi5 being analyzed, it has been included that there may be three twelve-face polyhedrons, nine octahedrons, six hexahedrons and thirty six tetrahedrons in an unit cell of LaNi5. The interstice radii of tetrahedron is smaller than that of hydrogen atom, so the tetrahedrons can not storage hydrogen. Then there will be 18 hydrogen atoms that can be storaged in an unit cell. This means that the ratio of hydrogen atom to metal atom is H/M=1. The maximum hydrogen capacity of LaNi5 is 1.379%.