Abstract: The lap joint of commercial purity titanium (TA2) and copper (T2) plates were successfully produced via friction stir welding technique,the macrostructure and microstructure of Cu/Ti lap interface were researched respectively. The mechanical properties of the joint were characterized by tensile shear tests as well. The results show that the defect-free lapwelds with well-formed surface and interface of joint were obtained when rotation speed and travel speed were 800 r/min,40 mm/min respectively. The interface of joint exhibited the typical bounded texture microstructure of Cu and Ti in the stir zone,and a region of swirling-like of bimetallic weld of TA2 titanium and T2 copper was formed. Moreover,mechanical interlock was formed in some parts of lap joint. A maximum failure load of 95% of the one of T2 copper was achieved, and the fracture location was located in the advancing side of copper, the fracture was the typical ductile fracture.