Abstract: In this paper,the microstructure and toughness of welded joints between austenitic manganese steel and rail steel by double flash butt welding were investigated by means of changing welding parameters, mechanical testing,examintion of microstructure with the optical microscope,electron microscope,X-ray diffraction,and electron probe analysis etc. Though investigation of microstructure and toughness in different zones of welded joints,a new method is proposed to improve HAZ toughness in side of rail steel on two dissimilar steel welded joint by flash butt welding. Our investigations have revealed that it is an effective method to weld austenitic manganese steel to rail steel using the intermediate materials. It is very difficult to weld austenitic steel to rail steel since they have quite different chemical composition and physical property.