Mg−6Zn−0.6Zr alloys with varying Ca contents (0, 0.6, 1.2, 1.8 wt.%) were prepared by gravity casting and hot extrusion. The effect of Ca content on the microstructure, mechanical properties, and ignition resistance of Mg−6Zn−0.6Zr alloy was investigated. The results show that Ca addition promotes Ca₂Mg₆Zn₃ phase formation while inhibiting MgZn₂ precipitation in as-cast alloys. After homogenization, the MgZn₂ phases are nearly dissolved, while numerous Ca₂Mg₆Zn₃ phases remain. During extrusion, the Ca₂Mg₆Zn₃ phases fragment, and MgZn₂ nanoparticles precipitate in the matrix. The combination of fine grains and high-density precipitates significantly enhances the strength of the Ca-containing alloys. The Mg−6Zn−0.6Zr−1.2Ca alloy exhibits the best overall mechanical properties, with ultimate tensile strength of 380.1 MPa, yield strength of 360.1 MPa, and elongation of 10.4%. Additionally, the ignition point increases from 556 to 824 °C with rising Ca content due to the formation of a dense CaO−MgO oxide layer.