Recently, hybrid laser-MIG welding technology has increasingly attracted interest in both industry and academia. By combining the two welding processes, it can modify the weld bead shape including the elimination of undercut, change the weld compositions, reduce the porosity, improve welding bridgeability, decrease the susceptibility of hot cracking, and increase welding speed. So far, the development of laser-MIG welding technology has been based on the trial-and-error procedure. In this paper, mathematical models and the associated numerical techniques have been developed to simulate the laser-MIG welding process. The transient keyhole dynamics, interaction between droplets and weld pool, and the shape and composition of the solidified weld were predicted for a three-dimensional moving laser-MIG welding. The heat and mass transfer and fluid flow in molten metal and temperature distribution inside the keyhole were studied. In the model, the volume-of-fluid (VOF) method was employed to track free surfaces. The Inverse Bremsstrahlung absorption of laser energy inside plasma, Fresnel absorption and the multiple reflections at the keyhole wall, and the thermal radiation by the plasma in the keyhole were all considered. Computer animations showing the fluid flow, weld pool dynamics, and the interaction between droplets and weld pool will be shown in the presentation.