The　effects　of　the　size　of　the　primary　phase　and　its　dispersion　on　the　refinement　and　microalloying　effect　of　Al-5Er　master　alloy　were　studied　by　refining　experiment,　microhardness,　SEM,　XRD　and　TEM.　The　results　show　that　the　primary　phase　Al3Er　can　produce　grain　refining　effect　when　the　additive　amount　of　Er　in　Al-5Er　master　alloy　is　0.1　wt　%.　After　plastic　deformation,　the　size　of　primary　phase　is　reduced,　the　dispersion　of　primary　phase　is　more　uniform,　and　the　refining　effect　is　further　improved.　After　ARB　three　times,　the　refining　effect　is　the　best　and　the　grain　size　of　alpha-Al　is　850　mu　m.　After　direct　aging　treatment,　the　hardness　of　the　pure　aluminium　sample　did　not　change.　After　solution　and　aging　treatment,　the　hardness　of　the　sample　reached　the　peak　in　15　min　of　aging,　and　the　increase　rate　of　microhardness　reached　51%,　which　was　attributed　to　the　precipitation　of　nanoparticle　Al3Er.