Abstract: Using experimental mechanical method of moiré analysis,strain field distributions of LY12CZ aluminum alloy welded joints under different conditions were investigated.The results show that moiré stripes of conventional welded joint just before fracture are not only few and scattered but also uneven,and the stress mainly concentrates on the poor position welded toes during the tensioning process with the relatively poor mechanical properties of welded joints.When the method of welding with trailing peening is adopted,moiré stripes of welded joint just before fracture are relatively thick and even due to the strengthening welded toes during the welding process,and fracture position transfers from the welded toes to weld,at the same time the mechanical properties of welded joints are improved greatly than conventional welding which can show that the technology of trailing peening is effective to strengthen welded joints of high strength aluminum alloy.