For developing cost effective damping Mg alloys with high damping capacity and better mechanical properties, the microstructures, the mechanical properties at room temperature and the damping capacity of Mg alloy adding CaO were investigated and compared with those of K1A alloy. CaO adding into pure Mg maintains the damping capacity and increases the ultimate tensile strength compared with those of pure Mg. Mg-CaO alloy can be regarded as cost-effective damping alloy with high damping and mechanical properties as well as with the advantages of improving oxidation and burning resistances. For developing cost effective damping Mg alloys with high damping capacity and better mechanical properties, the microstructures, the mechanical properties at room temperature and the damping capacity of magnesium alloy adding CaO were investigated and compared with those of K1A alloy. the damping capacity and increases the ultimate tensile strength compared with those of pure Mg. Mg-CaO alloy can be considered as cost-effective damping alloy with high damping and mechanical properties as well as with the advantages of improving oxidation and burning resistances.