The　quality　of　the　welding　or　defect　repair　of　metals　using　refill　friction　stir　spot　welding　(RFSSW)　is　fundamentally　influenced　by　material　flow.　The　welding　community　is　still　lack　of　comprehensive　understanding　of　the　flow　pattern　during　the　RFSSW　process　since　numerical　modeling　usually　has　its　own　compromises,　while　current　experimental　observations　of　such　solid-phase　material-flow　are　lack　of　precision　and　suffer　from　limited　visualization.　A　novel　experimental　material-flow　observation　method　is　proposed　to　chareactrize　the　dynamic　flow　behavior　by　mixing　a　few　another　alloy　with　the　same　matrix　into　the　welding　zone　as　a　tracing　of　the　flow　pattern.　Further,　the　process　was　combined　with　the　emergent　stops　at　different　stages　of　the　RFSSW　for　ease　of　analysing　the　dynamic　vertial　flow　pattern.　Meanwhile　the　deviation　angles　of　the　shear　textures　formed　in　the　welding　process　were　measured　and　calculated　for　determing　the　flow　orintation　in　the　horizental　planes.　During　the　plunging　stage,　the　flow-climbing　zone　and　flow-expansion　zone　were　observed,　with　the　initial　joint　connection　occurring　at　their　intersections.　The　threaded　sleeve　formed　an　outer　stirring　zone.　A　fan-shaped　expansion　zone　developed　between　the　flow-climbing　zone　and　flow-expansion　zone　during　tool　dwelling,　which　reduced　the　width　of　the　bonding　ligament.　When　the　threaded　sleeve　rotated　in　a　beneficial　direction,　the　generated　axial　thrust　mitigated　the　incomplete-refill　defects.　The　horizontal　material　flow　in　the　plunging　stage　gradually　aligned　with　the　ideal　shear　direction　from　top　to　bottom,　and　in　the　refilling　stage,　the　flow　aligned　more　closely　from　bottom　to　top.　Overall,　the　RFSSW　material-flow　patterns　at　different　stages　were　revealed,　which　could　provide　explanations　for　formations　and　fracture　mechanisms　of　three　distinct　hook　defects.　The　proposed　experimental　approach　for　analyzing　the　solid-state　material　flow　in　this　study　can　be　applied　to　investigations　of　similar　solid-phase　processes　and　help　to　optimize　the　tool　design.