Intra-body　communication　(IBC)　is　a　new,　different　＂wireless＂　communication　technique　based　on　the　human　tissue.　This　short　range　＂wireless＂　communication　technology　provides　an　alternative　solution　to　wearable　sensors,　home　health　system,　telemedicine　and　implanted　devices.　The　development　of　the　IBC　enables　the　possibilities　of　providing　less　complexity　and　convenient　communication　methodologies　for　these　devices.　By　regarding　human　tissue　as　communication　channel,　IBC　making　use　of　the　conductivities　properties　of　human　tissue　to　send　electrical　signal　from　transmitter　to　receiver.　In　this　paper,　the　authors　proposed　a　new　mathematical　model　for　galvanic　coupling　type　IBC　based　on　a　human　limb.　Starting　from　the　electromagnetic　theory,　the　authors　treat　human　tissue　as　volume　conductor,　which　is　in　analogous　with　the　bioelectric　phenomena　analysis.　In　order　to　explain　the　mechanism　of　galvanic　coupling　type　technique　of　IBC,　applying　the　quasi-static　approximation,　the　governing　equation　can　be　reduced　to　Laplace　Equation.　Finally,　the　analytical　model　is　evaluated　with　on-body　measurement　for　testing　its　performance.　The　comparison　result　shows　that　the　developed　mathematical　model　can　provide　good　approximation　for　galvanic　coupling　type　IBC　on　human　limb　under　low　operating　frequencies.