This　paper　discusses　the　grain　evolution　characteristics　of　friction　stir　welding　(FSW)　of　a　novel　Al-Cu-Mn-Er-Zr　alloy　at　different　welding　speeds.　It　focuses　on　the　dynamic　recrystallization　(DRX)　behavior　of　the　joint　and　the　evolution　of　precipitated　phases　in　each　region　at　a　welding　speed　of　200　mm/min.　Furthermore,　the　study　investigated　the　strengthening　mechanism　of　the　weld　joint,　which　was　augmented　by　an　aging　treatment　subsequent　to　the　welding　process.　The　results　indicate　that　the　grain　size　in　the　weld　nugget　zone　(WNZ)　is　significantly　refined,　with　the　average　grain　size　gradually　decreasing　as　welding　speed　increases.　As　the　distance　from　the　WNZ　decreases,　discontinuous　recrystallization　(DDRX),　continuous　recrystallization　(CDRX),　and　geometric　recrystallization　(GDRX)　occur　sequentially,　thereby　promoting　grain　refinement.　The　sequential　evolution　of　the　predominant　precipitated　phases　can　be　delineated　as　follows:　initially,　a　fine,　high-density　theta　＇　phase　is　observed　within　the　Base　Metal　(BM);　this　transitions　to　larger,　high-density　theta　＇　phases　within　the　heat-affected　zone　(HAZ).　Subsequently,　the　thermo-mechanically　affected　zone　(TMAZ)　exhibits　a　heterogeneous　distribution　of　theta　＇　phases,　culminating　in　the　formation　of　equilibrium　theta　phases　within　the　WNZ.　The　Er　elements　inhibit　the　growth　of　the　theta　＇　phase　by　aggregating　on　it,　demonstrating　a　synergistic　evolution.　Analysis　of　the　strengthening　mechanisms　reveals　that　the　key　factors　affecting　the　yield　strength　(YS)　of　the　joint　are　the　density　and　size　of　the　precipitated　phases.　These　findings　provide　a　new　perspective　for　the　study　of　Er　microalloying　in　Al-Cu　alloys.