The properties and microstructures after different annealing processes of an as-extruded ME magnesium alloy were investigated. The results showed the better properties with the tensile strength of 205 MPa and the elongation of 19.8%, respectively, could be obtained after annealing at 623 K for 4h and air-cooled, meaning that elongation value increased 40% than that of as-extruded sheets while the strength remained almost same. The annealing hold time corresponding with the higher elongation would shorten with the increase of annealing temperature. There is legible necking on broken tensile specimen. The behavior of fracture showed obvious characteristic of ductile rupture, with many tearing edges and cavities.