The microstructures, mechanical properties, and corrosion resistance of ZM21 magnesium alloys with a wide range of calcium(Ca) addition(0.1–1.6 wt%) were investigated. Results showed that the mechanical properties and corrosion resistance were improved with Ca addition because of grain refinement and formation of Ca_2Mg_6Zn_3. However,these properties were deteriorated when Ca contents reached 1.6 wt%. The optimal Ca content of alloys was 0.7 wt%; alloy with this Ca content showed good mechanical performance and corrosion resistance, having a strength of 260 MPa, an elongation of 21.5%, and an average weight loss of 0.77 mg/(cm~2 days). The results showed that the mechanical properties and corrosion resistance were improved with Ca addition because of grain refinement and formation of Ca2Mg_6Zn_3. However, these properties were deteriorated when Ca contents reached 1.6 wt%. The optimal Ca content of alloys was 0.7 wt%; alloy with this Ca content showed good mechanical performance and corrosion resistance, having a strength of 260 MPa , an elongation of 21.5%, and an average weight loss of 0.77 mg / (cm ~ 2 days).