Abstract: Laser melting treatment was carried out on the AZ31 magnesium alloy friction stir welded joint under different laser power （225, 270 W）. The effects of laser power on the microstructure, tensile properties and corrosion resistance of the fusion layer on heat-affected zone was studied. The results show that under different laser power, the microstructure of fusion layer was all fine columnar dendrites. At relatively low laser power, the depth and grain size of the fusion layer was small. After laser melting under different powers, the fusion layer mainly consisted of α-Mg phase and β-Mg₁₇Al₁₂ phase. At relatively low laser power, the content of β phase was high. Through laser melting treatment, the fusion layer achieved fine grain strengthening and second phase strengthening. At relatively low laser power, the tensile strength and percentage elongation after fracture were large, the tensile properties were good. The self-corrosion current density of fusion layer was small, the corrosion rate was slow, the self-corrosion potential was large, the corrosion tendency was small and the corrosion properties were good.