The　dynamic　mechanical　property　and　microstructure　evolution　in　localized　shear　deformation　was　investigated　in　the　Al-5.6%Mg-0.75%M-0.25%Er　alloy　cold　rolled　to　80%　reduction　by　using　Gleeble　3500　compression　at　the　strain　rate　of　0.01~500s-1.　The　results　show　that　both　a　critical　strain　rate　and　strain　were　required　for　the　formation　of　local　shear　band　under　high　strain　rate　compression.　The　initial　Lamellar　Boundaries(LBs)　in　the　matrix　region　are　parallel　to　the　rolling　direction(RD),　with　average　boundary　spacing　of　0.25μm;　The　LBs　within　the　shear　bands　region　have　a　angle　of　20°　with　RD,　whose　boundary　spacing　is　ranging　from　0.1　to　0.2μm.　The　LBs　gradually　rotate　to　an　angle　of　20°　with　RD　and　finally　become　wavy　shape　during　the　dynamic　deformation.　©　(2014)　Trans　Tech　Publications,　Switzerland.