Abstract: In this paper,the application and development of friction stir welding(FSW)in rail transit field are comprehensively reviewed from three aspects.Including the influence of tool geometry on welding process,FSW of multiple-unit train body parts and FSW of rail steel.The tool geometry can affect the heat generation and materials flow in FSW process,and subsequently affect the joint quality.Therefore,it is imperative to reasonably design the shape and size of the shoulder and pin,and the thread of the pin.At present,aluminum(Al)alloy is the predominant material used in multi-unit train body parts,and its FSW technique has been widely applied.With the increasing demand for lightweight in the field of vehicle manufacturing,magnesium(Mg)alloy is beginning to be used in some multiple-unit train body parts,which results in the FSW of Mg alloy become the future research aspect.What's more,the control mechanism of intermetallic compounds(IMCs)in Al/Mg dissimilar alloys is critical challenge.In the FSW of rail steel,the formation of martensite can be suppressed by adopting low rotating rate and welding speed.Which can meet the requirements of China railway industrial standard.In the future,it still need improve the welding efficiency.