The technical features and the development of Friction Stir Welding（FSW） were introduced in this paper. A thick FSW joint structure was illustrated for a car coupler panel structure of the high speed train. The mechanical property,fatigue property,bending property and metallographic structure of the FSW joints were compared with those of the double V-groove MIG butt joints in order to validate the properties of its welded joints. The results showed that the FSW joints had better performance than the MIG joints. The FSW can be used in the manufacture of the high speed train and the further research direction is also be proposed.