Intra-body　communication　(IBC),　using　the　human　body　as　the　channel　to　transmit　data,　has　lower　power　consumption,　less　radiation,　and　easier　linking　than　common　wireless　communication　technologies　such　as　Bluetooth,　ZigBee,　and　ANT(+).　As　a　result,　IBC　is　greatly　suitable　for　body　area　network　(BAN)　applications,　such　as　the　medical　and　health　care　field.　Furthermore,　IBC　can　be　implemented　in　wearable　devices,　including　smart　watches,　sports　bracelets,　somatic　game　devices,　and　multimedia　devices.　However,　due　to　the　limited　battery　capacity　of　sensor　nodes　in　a　BAN,　especially　implanted　sensor　nodes,　it　is　not　convenient　to　charge　or　change　the　batteries.　Thus,　the　energy　effectiveness　of　the　media　access　control　(MAC)　layer　strongly　affects　the　life　span　of　the　nodes　and　of　the　entire　system.　Certainly,　analyzing　MAC　layer　performance　in　a　galvanic　coupling　IBC　is　of　great　importance　for　the　overall　system.　To　obtain　the　attenuation　properties　of　IBC,　in　vivo　experiments　with　seven　volunteers　were　performed.　Meanwhile,　an　equalizer　was　used　to　compensate　the　frequency　distortion　in　consideration　of　frequency-selective　fading　characteristics　of　intra-body　channels.　In　addition,　a　comparison　of　the　bit　error　rates　(BER)　of　different　modulation　methods　was　carried　out　to　obtain　the　best　modulation　method.　Then,　the　attenuation　characteristics　of　intra-body　channels　were　applied　in　a　multi-node　physiological　signal　monitor　and　transmission　system.　Finally,　TDMA　and　CSMA/CA　protocols　were　introduced　to　calculate　the　bit　energy　consumption　of　IBC　in　the　practical　scenario.　With　stable　characteristics　of　the　intra-body　channels,　QPSK　with　an　equalizer　had　a　better　performance　than　the　tests　without　an　equalizer.　As　a　result,　the　modulation　method　of　FSK　could　achieve　a　lower　BER　in　lower　signal-to-noise　ratio　situations　and　an　FSK　method　with　TDMA　for　the　IBC　had　the　lowest　energy　consumption　under　different　practical　scenarios.