Abstract: Al-Mg-Sc-Zr high strength aluminum alloy was prepared by laser melting deposition at different scanning rates (3,4,5 mm · s⁻¹). The elemental burn loss behavior of Mg, Sc and Zr and defects formation mechanism were analyzed. The results show that with the increase of scanning rate, the average size and number of pores in the alloy increased. Under different scanning rates, Al, Mg, Sc and Zr were evenly distributed in the alloy. During deposition, the main burn loss form of Sc and Zr was oxidation, and their burn loss rates were not affected by the scanning rate; the main burn loss form of Mg was vaporization, and with the increase of scanning rate, laser energy density decreased, the Mg elemental burn loss rate increased first and then decreased.