Abstract: In this paper, a two-dimensional coupled mathematical model for heat transfer and flow of 2219 aluminum alloy electron beam welding pool was established based on finite volume method in Fluent software. In the model, the effects of surface tension, Marangoni shear force, hydrostatic pressure of fluid and recoil pressure of metal vapor were considered. In addition, formation and evolution of keyhole was traced by VOF (Volume of Fluid) algorithm. The results showed that the primary reason for the deepening of keyhole was the combination of recoil pressure's drilling and vortex's transportation. The decreasing heat source's power density caused the decreasing drilling velocity of recoil pressure. In addition, aluminum alloy spot welding experiment indicated that the numerical simulation result agreed well with the actual one.