Abstract: The high cooling rate of laser welding can easily form hard and brittle coarse columnar grains, and subsequent heat treatment can promote dislocation rearrangement and carbide dispersion precipitation, thereby refining grains, reducing internal stress, and improving the plasticity and fracture toughness of the weld. Therefore, research is being conducted on the modification of weld brittleness through post laser heat treatment of composite metal materials. Selecting aluminum alloy as the base material for welding composite metal materials, welding is achieved through laser welding technology with the assistance of welding rods. Design three different post weld heat treatment processes to modify the weld seam, and test the SEM images of the weld seam after each process treatment. Adjust the duration of solid solution insulation and analyze the changes in the mechanical properties, plasticity, and toughness of the weld after various process modifications, in order to analyze the brittle characteristics of the weld. The experimental results show that heat treatment process 2 can significantly reduce weld brittleness, improve toughness and ductility; As the solid solution insulation time increases, the grain size increases, leading to a decrease in mechanical properties. However, the mechanical properties of the weld after process 2 treatment are better. The initial stage of solid solution insulation treatment enhances the toughness of the weld, and if it is too long, it decreases. Heat treatment process 2 can reduce the brittleness of the weld and achieve weld modification.