Intra-body　communication　(IBC)　uses　the　human　body　as　the　transmission　medium　for　electrical　signals,　and　it　features　the　following　advantages:　low　power　consumption,　strong　anti-interference　ability,　high　data　security,　and　broad　application　scenarios.　However,　some　technical　issues　still　need　to　be　addresses,　such　as　the　choice　of　the　best　modulation　and　demodulation　scheme　in　different　application　scenarios,　influence　of　human　activity　on　IBC　performance,　variable　signal-to-noise　ratio　(SNR),　and　influence　of　transmission　distance　change　on　different　modulation　and　demodulation　methods.　This　paper　adopts　direct　sequence　spread　spectrum　(DSSS)　communication　and　phase　modulation　to　realize　DSSS-differential　phase　shift　keying　(DPSK)　and　DPSK　modulation　transmission　of　baseband　data.　Moreover,　the　Costas　loop　method　is　employed　to　achieve　reliable　symbol　recovery.　Under　the　same　conditions,　in　vivo　experiments　were　conducted　to　compare　the　performance　of　DSSS-DPSK　and　DPSK　galvanic　coupling　IBC　transceivers.　Notably,　these　transceivers　are　affected　by　the　changes　in　SNR,　transmission　distance,　and　human　activities.　Results　show　that　the　bit　error　rate　(BER)　of　the　DPSK　scheme　is　40　times　larger　than　the　DSSS-DPSK　scheme　in　a　30　cm　channel　length　and　different　SNR　experiments.　When　the　BER　performance　changes　from　extremely　poor　to　excellent　,　the　SNR　of　DSSS-DPSK　scheme　only　needs　to　be　improved　by　16　dB.　In　contrast,　when　the　BER　performance　changes　from　extremely　poor　to　good　,　the　SNR　of　DPSK　scheme　needs　to　be　improved　by　25　dB.　With　a　SNR　of　&　x2212;5　dB,　the　BER　ratios　of　the　DPSK　scheme　is　7　times　larger　than　the　DSSS-DPSK　scheme.　Also,　DSSS-DPSK　scheme　is　more　sensitive　to　changes　in　motion　status　than　DPSK.