The　influence　of　trace　Er　addition　on　high　pure　aluminum　was　studied　by　mechanical　properties　measurement,　hardness　measurement,　optical　microscope,　transmission　electron　microscopy　and　energy　spectrum　analysis.　The　results　show　that　minor　Er　in　the　studied　alloy　exists　in　the　form　of　Al3Er,　only　a　few　of　Er　in　α-Al　based　solid　solution.　Primary　Al3Er　particles　formed　during　solidification　are　often　found　at　the　center　of　aluminum　grains　and　act　as　heterogeneous　nucleus,　also　increase　the　rate　of　nucleation,　therefore　the　grains　are　remarkably　refined.　Trace　Er　addition　to　high　pure　aluminum　is　able　to　improve　its　mechanical　properties,　which　is　caused　by　fine　grain　strengthening,　substructure　strengthening　and　precipitation　strengthening.　The　recrystallization　temperature　of　Er-doped　aluminum　can　be　increased　by　50°C,　which　is　caused　by　the　pinning　effect　of　highly　dispersed　fine　Al3Er　precipitates　on　dislocations　and　sub-grain　boundaries.