The　effects　of　Al–0.5Er–0.2Zr　and　Al–1Er–0.25Zr　(wt%)　alloys　on　the　grain　size　of　high-purity　aluminum　after　isothermal　aging　at　450　°C　were　studied　by　micro-hardness,　scanning　electron　microscopy　(SEM),　optical　microscopy,　and　transmission　electron　microscope　(TEM).　The　experimental　results　showed　that　the　Al3Er　secondary　phases　precipitated　uniformly　after　isothermal　aging　of　Al–0.5Er–0.2Zr　alloy.　The　content　of　Er　element　in　Al–1Er–0.25Zr　alloy　was　much　larger　than　the　maximum　equilibrium　solid　solubility　in　aluminum.　The　primary　phase　was　densely　distributed　in　the　matrix.　In　addition,　a　large　number　of　Al3Er　and　Al3　(Er,　Zr)　phases　matched　with　the　matrix　lattice　have　been　precipitated　during　heat　treatment.　The　heat-treated　master　alloys　were　added　to　the　high-purity　aluminum　liquid,　and　the　nucleation　sites　were　provided　by　the　micron-sized　and　nano-sized　precipitation　phases.　At　last,　the　average　grain　size　obtained　by　the　refinement　experiment　was　less　than　300　μm.　At　the　same　time,　the　reasons　for　the　refinement　effect　of　the　interaction　between　Er　and　Zr　elements　were　preliminarily　analyzed.　©　2019,　Springer　Nature　Singapore　Pte　Ltd.