The relationship between parameters and tensile strength of CMT+P welded 2 A97 Al-Li alloy is established by quadratic rotary unitized design,and the influences of welding parameters on the mechanical properties of welded joint are investigated by metallographic microscope,scanning electron microscopy and tensile testing machine. Experimental results show that the range of optimized welding parameters can be determined according to the regression equation,in this range,the weld is well formed,and the tensile strength exceeds60% of the base metal. The tensile fracture occurs in the bond line zone with ductile-brittle mixed mode,and the transition zone between equiaxed fine grain and columnar crystal becomes the weakest link of the joint.