Abstract: Lap joints of 5A90 aluminium-lithium alloy were welded with refill friction spot welding process,in which the process parameters were changed for different purpose.The joint mechanical test of lap shear samples and cross tension samples, metallography analysis and joint microhardness test were carried out.The experimental results indicate that 1.5 mm thickness spot welded joint shear strength is more satisfying with tool rotation speed of 1800 r/min and welding time of 1.5 s.The cross tension test results shows thats the joint strength of cross tension increases with welding time,and insensitive to the change of weding tool rotational speed and press depth.The joint cross section metallograph show that the joint vertical interface is the weak joining area.The microhardness distribution indicates that the joint weak microzone locates in joint horizontal interface.