By studying welding technology of full penet-ration X-shped weld in butt joint between cast steels G20 Mn5 and S355 J2 W for the braking hanging bracket in boige in the double-decker train for Sydney project,the macro metallo-graphy and mechanical properties of welded joint are analyzed,such as tensile, bending, impact and hardness. By formulating a reasonable welding process,comparing and analyzing the exp-erimental results of symmetric and asymmetric welding tech-nologies,a set of welding technology method is summarized,which meets the quality requirment,has short auxiliary time and strong operability,and improves the quality and efficiency. This method relaizes the full penetration butt welding of dissimilar materials of cast steel and weathering resistant steel,and provides basis and experience for bogie production.