Optimum process parameters of laser beam welded T joints for 2524 and 7150 aluminum alloys are investigated in this paper. The microscopic structure and mechanical properties for T joints are studied by metallographic analysis, microhardness and tensile test. Test results show the grain in welding seam is fine and dense.The microhardness is lowest in welding seam. The tensile properties for joints in x direction is 384 MPa, while in z direction is 236 MPa.