<p>Introducing mechanical vibrations into gas metal arc welding (GMAW) can bring a variety of beneficial effects. However, due to the lack of quantitative data supporting the heat and mass transfer in the molten pool, the relevant fundamental physical processes have yet to be thoroughly investigated. This study investigates the influence of vibration frequency on the heat and mass transfer in the molten pool during vertical mechanical vibration welding through numerical and experimental methods. A three dimensional transient heat and mass transfer model has been established for the first time, taking into account the vertical vibration force and the welded plate movement.The results indicate that compared with the GMAW, more superheating molten metal is transported to the molten pool rear in the former half of the vibration-assisted gas metal arc welding (V-GMAW) molten pool. The molten pool cooling rate in V-GMAW is faster than that in GMAW. The intensity degree in the molten metal flow within the molten pool increases following the application of mechanical vibrations. In the front half of the V-GMAW molten pool, the molten metal experiences stronger driving forces due to the applied vibration. An increased number of vortices was observed in the latter part of the molten pool, along with an enhancement in their intensity and an expansion of their effective range. With the vibration frequency increase, more superheating molten metal is transported to molten pool rear, and the vortices intensity and effective range in the latter half of the weld pool increase.</p>