CO2 Laser welding of 5A02 and 5A06 aluminum alloys sheet with different thickness is performed with or without the addition of filler metal powder . The main factors affecting welding process stability and formability of weld are investigated. Meanwhile, based on the finite element analysis (FEA), temperature field and the stress-strain field of aluminum alloy with different thickness on laser welding are simulated. The residual stresses distribution and deformation features of tailored welded blanks (TWB) are analyzed. The results indicate that with the increasing of magnesium in aluminum alloys, the absorptivity is also improved, so a stable welding process can be obtained for a higher content of magnesium in aluminum alloys. The addition of the metal powder can enhance the energy coupling efficiency during laser welding of aluminum alloys sheet with different thickness, and the weld formation and process stability can be improved greatly. The simulated results indicate that temperature field distribution is unsymmetrical. The distributions of the stress-strain are also asymmetric. The distributions of pulling stress field in the thinner plate are larger than that in the thicker one and the deformations in thinner plate are more serious than that in thicker one.