The　metallic　substrate　of　commercial　REBCO　tapes　from　eight　different　manufacturers　has　been　systematically　investigated.　Tensile　properties　at　both　room　temperature　and　77　K　were　measured.　The　grain　morphology,　size,　orientation,　dislocation　density,　and　internal　stress　of　the　grains　on　both　the　cross-section　and　surface　of　each　tape　were　studied　using　EBSD.　After　an　in-depth　analysis　of　the　relationship　between　yield　strength　and　grain　size,　elemental　composition,　dislocation　density,　and　twin　boundaries,　it　has　been　preliminarily　confirmed　that　dislocation　density　is　a　possible　dominant　factor　in　determining　the　yield　strength　of　the　metallic　substrate　of　commercial　REBCO　tapes.The　kernel　average　misorientation　value　(KAM)　of　the　cross-section　could　be　one　of　the　best　indicators　for　evaluating　yield　strength.　Based　on　this　analysis,　potential　methods　for　enhancing　yield　strength　are　also　briefly　discussed.　This　investigation　aims　to　provide　valuable　insights　for　researchers　to　better　understand　the　mechanical　properties　of　REBCO　tape.