The composite structure of aluminum alloy and steel has the characteristics of light weight, high strength and low cost. It plays an important role in aerospace, shipbuilding, automobile manufacturing and other fields, obtaining reliable and stable aluminum/steel composite structure is the requirement of the times. Friction stir welding (FSW), as a new type of solid phase bonding technology, has the advantages of high efficiency, energy saving and environmental protection. In the regular friction stir welding process of aluminum/steel dissimilar metals, it needs enough welding axial force and stirring head torque to generate heat for welding. In this process, it will lead to the wear of the stirring head and seriously limit the welding speed. Based on the optimization of aluminum/steel dissimilar metal friction stir welding, this paper summarizes the external auxiliary methods that have made progress in aluminum/steel friction stir welding at present, and divides them into mechanical structural external auxiliary FSW, intermediate transition layer auxiliary FSW, temperature controll external auxiliary FSW and ultrasonic vibration auxiliary FSW. On this basis, the development direction of external auxiliary aluminum/steel dissimilar metal friction stir welding is further prospected.