The　tensile　strength　and　impact　properties　at　low　temperature　were　investigated　on　Al-6Mg-0.8Zn-0.5Mn-0.2Zr-0.2Er　alloy　for　cold　rolled,　warm　rolled　and　fully　annealed　samples.　The　original　microstructures,　tensile　fracture　and　impact　fracture　were　observed　using　electron　back-scattered　diffraction　(EBSD),　transmission　electron　microscope　(TEM)　and　scanning　electron　microscope　(SEM)　in　order　to　analyze　the　effects　of　microstructure　on　tensile　property　and　impact　properties.　The　results　show　that　with　the　decreasing　of　testing　temperature,　the　stresses　are　drastically　increased　as　well　as　the　impact　properties.　The　warm　rolled　alloy　with　more　sub-boundaries　has　a　higher　strength　and　impact　property,　which　realizes　the　matching　of　high　strength　and　toughness.