Good ignition-proof principle and mechanical properties were realized in Mg-Y-Ca-Zr alloy system.By adding Y and Ca elements,the ignition point of Mg-3.5Y-0.8Ca alloy was improved to over 1173 K,and the alloy could be melted in air without any protections.The effect of Zr addition on the microstructures and mechanical properties of Mg-3.5Y-0.8Ca alloys were investigated,and Mg-3.5％Y0.8％Ca-0.4％Zr alloy had good comprehensive properties with tensile strength of 190 MPa and elongation of 11％.Auger electron spectroscopy (AES) and X-ray diffraction (XRD) analysis revealed that the oxide film formed on the surface of Mg-3.5Y-0.8Ca alloy was mainly composed of Y2O3.Thermogravimetric measurements in dry air indicated that the oxidation dynamics curves measured at 773,873 and 973 K followed the cubic law.Moreover,the semiconductor characteristic of Y2O3 film and its effect on ignition-proof properties of Magnesium alloys were discussed from the viewpoint of electrochemistry.