In　galvanic　coupling　conductive　intracardiac　communication(GCCIC)　of　the　leadless　pacemaker,　the　electrical　signal　transmitted　directly　through　the　myocardium　and　blood　is　inevitably　affected　by　the　cardiac　cycle.　The　existed　research　paid　more　attention　to　the　effect　of　the　myocardium　during　communication.　However,　experiments　show　the　change　of　blood　volume　also　has　a　great　impact　on　signal　transmission.　In　this　paper,　the　cardiac　cycle　is　divided　into　seven　phases　with　different　blood　volumes　periodically,　and　the　signal　gain　is　monitored　through　a　homemade　dynamic　measurement　platform　with　two　peristaltic　pumps　and　several　silicone　tubes.　Through　in　vitro　experiment　of　the　porcine　heart,　the　changes　of　two　channel　gains　caused　by　the　cardiac　cycle　are　analyzed.　The　results　show　that　channel　gains　change　periodically　with　the　change　of　blood　volume　in　the　cardiac　cycle,　and　the　change　trends　of　the　two　channels　are　different　because　the　signal　paths　in　the　two　channels　are　different.　For　the　Right　Ventricle　-　Right　Atrium　channel,　gain　varies　from　-62　to　-47　dB　and　channel　gain　is　inversely　correlated　with　blood　volume.　For　the　Right　Ventricle　-　Left　Ventricle　channel,　when　blood　volume　is　less　than　80　mL,　channel　gain　is　about　-51　dB.　And　when　blood　volume　is　greater　than　80　mL,　channel　gain　fluctuates　around　-48　dB.　This　study　shows　the　gain　of　the　intracardiac　communication　channel　is　affected　by　the　change　of　blood　volume　in　the　cardiac　cycle.　©　2022　IEEE.