Abstract: According to T Joint of weathering steel plate with 2.5 mm and 3 mm in thickness, large tilt angle laser welding with filler wire of ER50-G was used. The fatigue properties of welded joint, at the optimized welding parameters were tested, and then the macro and micro characteristics of the fractures were analyzed. The results show that the fatigue strength of the welded joint is 222.5 MPa, the specimens fracture in the weld toe, where there is the higher stress concentration and which is the main reason of fracture. There is a typical fatigue characteristics in the initiation zone and propagation zone of the crack, the size of the propagation zone increases with fatigue cycles, and the micro characteristics of the final fracture zone are dimples. The results will support the application of the laser welding with the wire on the body structure of high speed train.