Abstract: Laser shock peening (LSP) was carried out on wire and arc additive aluminum alloy samples, phenomenon of laser shock peening on arc additive aluminum alloy was observed, and effect of laser shock peening on microstructure and mechanical properties of arc additive aluminum alloy was analyzed. After laser shock peening, microstructure of unaffected zone was similar to that of arc additive samples, which was composed of slender columnar grain zone and fine equiaxed grain zone between columnar grain zones. Medium sized equiaxed grains and long columnar grains were scattered in affected zone. Laser shock changed microstructure of material, medium-sized equiaxed crystals appeared, and pores were reduced. After LSP, residual compressive stress field was generated on the surface of additive aluminum alloy, and the maximum residual compressive stress could be obtained under reasonable process parameters. Under different experimental parameters, increase of impact energy, impact times and lap ratio could increase microhardness and influence depth of aluminum alloy. It was proved that LSP significantly improved surface properties of arc additive aluminum alloy samples, and played an important role in improving mechanical properties.