Abstract: From the viewpoint of macroscopic phenomena in heat transfer, a combined “double-ellipsoid + linearly-increased peak value cylinder” volumetric heat source distribution mode was proposed according to the characteristics of laser + GMAW hybrid heat source welding process. A finite element model of laser + GMAW hybrid heat source welding process was established. The temperature distribution, and the size of the weld cross-section were numerically calculated. It can be observed that the calculated results were in good agreement with the experimental results, which proves the rationality and applicability of the combined volumetric heat source model. And then, the calculated temperature field was utilized for the numerical modeling and comparison of the welding deformation and residual stress between GMAW and laser + GMAW hybrid welding process. The results shown that the heat input, weld width, welding deformation and high residual stress region of laser + GMAW hybrid welding were all much smaller than that of GMAW with the identical weld pool depth. The research confirmed the advantages of laser + GMAW hybrid welding, and provided basic theoretical data for the optimization of process parameters.