Abstract: Aiming at the deficiencies of the traditional weld technology on aluminum alloys, laser welding was put forward.Through metallographic analysis on the weld of Al-5Mg-0.3Sc, tensile strength and micro-hardness test, technological parameters of laser were studied to improve the performance of the weld.The results show that because of rare Sc, weld without air holes and cracks can be obtained in the conditions of pretreatment, reasonable laser power, scanning velocity and the flow of shielded gas, which the sizes of center grains are 1/11 as large as that of substrate, micro-hardness achieves 95% and tensile strength achieves 88% of substrate's.