Hot-rolling　plates　of　Al-4.5Mg-0.7Mn-0.2Zr-0.2Er　alloy　were　prepared　under　the　reduction　of　50%,　and　tensile　property,　impact　toughness　were　measured　at　the　temperatures　varying　from　200-470　degrees　C.　The　microstructure　of　the　hot-rolling　plates　was　investigated　using　scanning　electron　microscopy　and　transmission　electron　microscopy.　The　results　showed　that　the　tensile　strength　and　yield　strength　decreased　with　the　rise　of　the　hot-rolling　temperature,　the　elongation　and　impact　toughness　showed　the　opposite　trend,　and　the　best　match　between　strength　and　toughness　was　at　the　rolling　temperature　of　350　degrees　C.　The　second　phase　particles　in　the　alloy　had　a　great　influence　on　the　impact　toughness　and　plasticity　of　the　alloy.　As　the　rolling　temperature　increased,　the　dynamic　recovery　and　dynamic　recrystallization　occurred　in　the　alloy.　Dispersed　Al-3(Er,　Zr)　particles　formed　in　the　alloy　when　Er　and　Zr　were　added.　The　Al-3(Er,　Zr)　particles　were　able　to　pin　dislocation　motion,　hinder　the　growth　of　subgrains　and　the　migration　of　grain　boundaries,　thereby　inhibited　the　dynamic　recrystallization　of　Al-4.5Mg-0.7Mn-0.2Zr-0.2Er　alloy　and　its　thermal　stability　improved.