The　use　of　wireless　networked　miniaturised　medical　implants　is　promising　a　significant　leap　forward　in　health　monitoring　and　medical　treatment.　In　contrast　to　conventional　wireless　communication　which　takes　place　over　the　air,　implant　communication　through　the　body　poses　unique　challenges.　Considering　there　is　less　literature　available　on　out-to-in　and　in-to-out　propagation　mechanisms　on　the　different　tissue　interfaces　for　deep　implant　communication,　in　this　study,　the　multi-layered　planar　model　and　the　mathematical　equations　of　multiple　incidence　are　proposed　to　calculate　and　analyse　some　key　transmission　characteristics　of　body　channel.　The　authors　take　human　arm　as　the　research　object,　and　compute　four　cases　of　electromagnetic　wave　normal　incidence　on　multi-layer　human　body　tissues　with　different　positions　of　the　deep　implant　at　the　frequency　of　10　Hz-100　GHz.　They　also　establish　a　simulation　model　of　normal　incidence　on　three-layer　human　body　tissues　at　a　frequency　of　2.45　GHz　based　on　the　finite-element　method　in　COMSOL　Multiphysics.　The　relative　differences　in　simulation　results　are　all　＜3.14%,　which　show　a　good　agreement　with　the　theoretical　calculation　results.