Abstract: Based on SYSWELD finite element software, an efficient calculation method based on instantaneous heat source was developed to simulate the welding residual stress of complex aluminum alloy structures. Firstly, the moving heat source and instantaneous heat source were respectively used to simulate the residual stress of 6061 aluminum alloy plate surfacing welding joint and compared the results, which verified the effectiveness of the newly developed method. Subsequently, the developed efficient calculation method was used to simulate the welding transient stress and welding residual stress of 6 000 series aluminum alloy complex structure so as to analyze the causes of cracks generated in actual product manufacturing. The result shows that the high transient tensile stress is generated at this position during the welding process lead to cracking of the aluminum structure. The simulation result indicates that both solutions can improve the welding transient stress and residual stress to a certain extent, and increasing the thickness of the profile shows better improvement effect.