Abstract: Al-Mg-Sc-Zr alloy thin-walled parts were prepared by laser selective melting. The homogeneity of microstructure and tensile properties of Al-Mg-Sc-Zr aluminum alloy in different regions were studied, and the cavity nucleation and growth behavior during stretching were analyzed. The results show that the microstructure of the bottom and top regions of the thin-walled part had typical bimodal microstructure features composed of columnar coarse crystals and equiaxed fine crystals, the coarse grain〈100〉orientation were significantly parallel to the deposition direction, the fine grain were approximately randomly oriented, and the size and distribution of microdefects such as pores were similar. The change of stress with strain in different regions of the thin-walled parts during tension perpendicular and parallel to forming direction was similar. The strength and percentage elongation after fracture during tension perpendicular to forming direction were slightly higher than those during tension parallel to forming direction, but the increment was less than 5%, indicating the tensile properties were approximately isotropic. In tensile deformation, cavities tended to nucleate and grow in the fine grain region.