Abstract: Friction stir welding is a solid-state welding technique,which may offer a new solution for thick copper plate joining.Friction stir welding of T2 copper plate,25 mm in thickness,was completed successfully by single pass welding,and the microstructure,physical property,electrical property and energy spectrum of the T2 copper joint were analyzed.The experiment results demonstrate that the appearance of the joint is good and the inner in the joint is detect-free under optimum joining conditions.When the rotating speed is 960 r/min and the welding speed is 70 mm/min,the tensile strength of the joint reaches 186.6 MPa,and the conductivity of the joint is approximately equal to that of the base metal.