Mechanical properties of as-cast and as-extruded Mg-7Zn-3Al-0~0.7Re(wt%) magnesium alloys both at room temperature and elevated temperatures were compared by means of TEM, SEM, EDS and tensile mechanical property testing, and the effects of rare-earth addition and deformation on the strength and plasticity of the alloys were analyzed. The results show that the proper addition of Er could dramatically increase the elevated temperature plasticity of as-cast Mg-Zn-Al alloy, while it would not change much the room temperature mechanical properties and the elevated temperature yield strength. It is also revealed that spherical nano-precipitates occurred during the extrusion, which increased the elevated temperature mechanical properties of the as-extruded Mg-Zn-Al-Er alloy remarkably. Compared to those of the as-cast alloy, the yield strength and elongation of the as-extruded alloy at 200 °C were increased by 105% and 120%, respectively. Furthermore, fractographs present an obvious tough fracture feature