The　hot　deformation　behaviors　of　as-solution　Mg-xZn-yEr　alloys　(x/y=　6,　x=3.0,　4.5　and　6.0;　y=0.50,　0.75　and　1.00)　were　investigated　on　Gleeble-1500　thermal　simulator　in　a　temperature　range　of　200-450　degrees　C　at　a　strain　rate　of　0.001-1　s(-1).　The　true　stress-strain　curves　showed　the　dynamic　competition　between　the　working　hardening　and　working　softening　mainly　due　to　the　dynamic　recrystallization　(DRX)　occurring　during　hot　compression.　The　constitutive　equations　were　constructed　which　could　accurately　predict　the　peak　stress　of　the　alloys.　The　addition　of　Zn　and/or　Er　resulted　in　higher　deformation　activation　energy　for　Mg-3Zn-0.5Er　(　alloy　A).　The　processing　maps　were　constructed　as　function　of　the　temperature　and　the　strain　rate,　providing　the　optimum　hot　working　conditions　(i.e.,　at　strain　of　0.3,　Mg-3Zn-0.5Er　(alloy　A):　380-430　degrees　C,　＜0.1　s(-1);　Mg-4.5Zn-0.75Er　(　alloy　B):　380-　450　degrees　C,　0.01-0.1　s(-1);　Mg-6Zn-1Er　(alloy　C):　390-　440　degrees　C,　0.01-0.1　s(-1)).　The　as-solution　treated　Mg-4.5Zn-0.75Er　(alloy　B)　demonstrated　more　optimum　hot　working　window　comparing　with　Mg-3Zn-0.5Er　(alloy　A)　and　Mg-6Zn-1Er　(alloy　C).