Abstract: In order to explore the influence of length of austenitic stainless steel welding insert on the flash welding performance of rail steel-high manganese steel frog，taking the flash welded joints with different insert lengths as the research objects, the mechanical properties and microstructure of the rail steel-high manganese steel frog flash welded joints were analyzed by means of mechanical property tests, metallographic tests, electron microscope observation and other methods.The results show that the tensile strength of the flash welded joints presents a negative correlation trend with the post-welding length of the insert, while the impact absorption energy presents a positive correlation trend with the post-welding length of the insert. There are differences in the thermal impact and upsetting force received by the flash welded joints with different insert lengths during the welding process. The joints with a shorter insert length are relatively more severely affected, resulting in differences in the microstructure morphology characteristics of the insert area.