The　electronic　structure　and　magnetic　properties　of　the　Ruddlesden-Popper　(RP)　layered　perovskite　Bi8Ba4Mn8O28　were　investigated　by　using　the　projector　augmented　wave　(PAW)　pseudopotentials　method　based　on　the　density　functional　theory.　Due　to　the　substitution　of　Ba　in　the　A　site,　the　rotation　and　tilt　of　the　MnO6　octahedra　could　be　approved,　and　their　impact　on　the　electronic　structure　and　magnetic　properties　were　also　discussed.　The　generalized　gradient　approximation　calculation　with　the　correction　of　the　onsite　Coulomb　interaction　(GGA　+　U)　showed　that　the　ground　state　of　Bi8Ba4Mn8O28　is　a　ferromagnetic　half-metal　with　a　half-metallic　gap　of　3.　07　eV　and　a　total　magnetic　moment　of　31μB.　The　magnetic　moment　of　Bi8Ba4Mn8O28　is　mainly　contributed　by　the　magnetic　moment　of　Mn　atoms,　while　the　magnetic　moments　of　Bi,　Ba,　and　O　atoms　are　relatively　small.　The　half-metallicity　is　mainly　due　to　the　large　exchange　splitting　between　the　spin-up　and　spin-down　electrons　of　Mn　3d　states.　When　the　lattice　constants　vary　in　a　wide　range　of　-　10%　to　14%,　the　half-metallicity　can　be　maintained　and　the　total　magnetic　moment　of　the　unit　cell　is　always　kept　at　31μB　©　2024　Beijing　University　of　Technology.　All　rights　reserved.