Based on dimension acquisition of structured light 3 D-Scanning technology, data processing and reverse reconstruction of Geomagic, and slicing and path planning of AMSlicer Pro, the lacking part of thin-wall aluminum alloy ZL114 A was modeled in reverse. Through arc additive manufacturing and repair with welding wire ER4043, the lacking part was repaired perfectly. The means of nondestructive testing, microhardness tester, electronic universal testing machine and scanning electron microscopy were used to study and analyze the microstructure and performance of the repaired part in arc additive manufacturing and repair. The results show that the surface of repaired sample has no surface-breaking defect, and the internal microstructure is dense without visible defects. The microhardness at the top of repaired sample is a bit higher than that at the bottom, and the microhardness in the middle part is stable. The mechanical properties of the sample parallel to the direction of arc cladding are superior to those perpendicular to the direction of arc cladding. Therefore, the mechanical properties of repaired sample are anisotropy. The Al-Si eutectic structure of repaired sample showing fine strips distributes in α solid solution, and extends from bottom to top. The Al-Si eutectic structure at the top of repaired sample disperses and has small cutting effect onα matrix, which makes the properties of Al-Si eutectic at the top better than those at the bottom.