The　phase　structure,　grain　refinement,　and　microalloying　effect　of　the　Al-5Er-Ti　master　alloy　were　analyzed　by　a　refining　experiment,　microhardness　test,　OM,　SEM,　and　XRD.　The　results　show　that　when　the　Er/Ti　atomic　ratio　is　2.7,　the　refining　effect　of　the　Al-5Er-0.5Ti　master　alloy　is　significantly　better　than　Al-5Er,　which　is　due　to　the　Ti2Al20Er　phase.　There　are　three　crystal　orientations　of　Ti2Al20Er　and　alpha-Al　that　satisfy　the　E2E　model,　among　which　(620)Ti2Al20Er＜260＞Ti2Al20Er//(111)Al＜110＞Al　is　the　least　mismatched　one.　When　the　Er/Ti　atomic　ratio　is　reduced　to　below　1.3,　the　Ti-containing　phase　of　the　Al-5Er-Ti　master　alloy　is　composed　of　Ti2Al20Er　and　Al3Ti.　The　primary　phase　size　of　the　Al-5Er-1.5Ti　master　alloy　decreases　with　the　increase　in　cooling　rate,　and　the　grain　refining　effect　improved　more　significantly.　The　optimum　size　of　the　Ti2Al20Er　phase　and　Al3Ti　phase　is　6.0　mu　m　and　9.5　mu　m,　respectively.　The　grain　size　of　pure　aluminum　is　reduced　from　14,000　mu　m　to　300　mu　m　by　Al-5Er-1.5Ti　master　alloy　refinement,　and　the　refinement　rate　is　97.9%.　Direct　aging　of　the　refined　sample　did　not　have　a　precipitation　strengthening　effect.　After　the　solution　and　aging　treatment,　the　peak　aging　of　the　refined　sample　was　reached　in　15　min,　and　the　microhardness　increased　by　41%.