Abstract: In view of the insufficient toughness of the GPa-grade deposited metal, four groups of welding wires were designed to study the effects of Al and Mg elements on the microstructure and mechanical properties of metal cored welding wires. The microstructure of the deposited metal was characterized by scanning electron microscopy (SEM). The mechanical properties of the deposited metal were characterized by mechanical properties test. The results show that the deposited metal mainly consists of martensite and bainite. With the increase of Al and Mg contents from 0Al-0Mg to 0.3Al-0.9Mg, the content of O decreases from 0.030 8% to 0.014 3%, and the content of coalesced bainite decreases while that of lath martensite increases. and the inclusions were transformed from traditional oxides including Fe, Al, Si, Mn, etc. to spherical and fine particles mainly composed of Al and Mg oxides inclusions. Compared with 0Al-0Mg group, the average size of the inclusion in 0.3Al-0.9Mg group decreases by 0.13 μm, the tensile strength was increased by 152 MPa, and the impact absorption energy was increased by 11 J (−20 ℃).