The　effect　of　stationary　shoulder　friction　stir　welding　(SSFSW)　on　temperature　gradient　and　material　flow　was　investigated　to　optimize　the　SSFSW　process.　A　three-dimensional　numerical　model　of　heat　generation　and　material　flow　was　established　by　using　computational　fluid　dynamics,　and　thermo-physical　phenomena　of　SSFSWed　Ti-6Al-4V　were　quantitatively　analyzed　in　terms　of　heat　generation,　heat　transfer,　material　flow　and　viscosity.　The　temperature　gradient　was　more　uniform　in　a　narrow　stir　zone　produced　by　the　SSFSW　process.　The　distribution　of　velocity　was　studied,　and　instantaneous　velocity　center　of　tool　was　divided　into　two　different　velocity　regions　to　study　the　material　flow.　The　simulation　results　were　verified　by　experimental　thermal　cycles　of　calculated　position　of　model,　which　was　in　accordance　with　the　experimental　results.