Based　on　the　intra-body　communication　by　galvanic　coupling,　this　paper　aimed　to　explore　the　impact　on　the　signal　transmission　in　the　human　body　when　the　muscles　were　under　the　stress,　and　investigated　the　channel　characteristics　of　different　transmission　distance　and　different　grip　size　of　the　human　arm.　The　results　showed　that,　in　the　short-distance　channel,　the　stressed　muscles　hindered　the　signal　transmission　and　in　the　long-distance　channel,　the　stressed　muscles　promoted　the　signal　transmission.