Intra-body　communication　(IBC)　is　a　new,　emerging,　short-range　and　human　body　based　communication　methodology.　It　is　a　technique　to　network　various　devices　on　human　body,　by　utilizing　the　conducting　properties　of　human　tissues.　For　currently　fast　developed　Body　area　network(BAN)/Body　sensor　network(BSN),　IBC　is　believed　to　have　advantages　in　power　consumption,　electromagnetic　radiation,　interference　from　external　electromagnetic　noise,　security,　and　restriction　in　spectrum　resource.　In　this　article,　the　authors　propose　an　improved　mathematical　model,　which　includes　both　electrical　properties　and　proportion　of　human　tissues,　for　IBC　on　a　human　limb.　By　solving　the　mathematical　model　analytically　on　four-layer　system　(skin,　fat,　muscle,　and　bone)　and　conducting　in-vivo　experiment,　a　comparison　has　been　conducted.