Abstract: Regarding the 3mm thick plate used in the Fuxing high-speed train with a speed of 350 kilometers per hour, laser wire filling welding process tests were conducted on the butt joints using 5087 welding wire under the optimal welding process parameters. Fatigue performance tests were also conducted on the welded test plates. By observing the macroscopic morphology of the test plate fracture and the microscopic morphology in the scanning electron microscope photos, the fracture characteristics of the fracture were analyzed. The fatigue limit of the 3II joint was determined by lifting and lowering the engine. The results show that when the number of cycles is 1 * 107 times (specified life), the median fatigue limit σ 0.1 of the 3II joint of 6082-T6 aluminum alloy laser wire filling welding is 87.5MP; Most fatigue specimens fracture in the heat affected zone of the base metal, as this location undergoes HAZ grain growth and strengthening phase particle growth precipitation under welding thermal cycling; The fatigue pattern of the fractured specimen is clear, and it is clearly visible in both the crack initiation zone and the crack propagation zone, while exhibiting characteristic fracture characteristics. As the number of cycles gradually increases, the range of the propagation zone also gradually expands. Fatigue cycles are the fundamental cause of fracture, and the dimple shaped fracture surface texture is a common feature of the final fracture zone of the fractured specimen. The experimental results provide technical assistance for the application of laser wire filling welding in the long components of aluminum alloy vehicle bodies.