To avoid the angular deformation of T joint in high-strength aluminum alloy plate of large aircraft, a method that equips skin back with auxiliary heat source (AHS) is proposed to prevent angular deformation effectively. A welding model applicable to this welding method is developed based on finite element software ABAQUS, the material and geometrical nonlinear finite element methods and the thermal-elastic-plastic finite element method for moving heat source are applied to simulate the thermodynamic coupling behavior as well as to analyze the temperature field, residual stress and welding deformation in welding process. The deformation of the weld joint before and after the addition of the AHS is measured by experimental method. The findings show that the flexural deflection and angular deformation achieved through numerical computation completely consist with the experimental result, which has proved the effectiveness of the finite element methods developed.