With the three-dimensional transient thermal flow coupled finite element model of laser welding, the three-dimensional keyhole morphology and metal flow characteristics of the molten pool during the process of the droplet entering the molten pool at different droplet filling positions were studied. Numerical simulation results show that the droplet filling position had a significant effect on the three-dimensional morphology of keyhole and the flow behavior of molten pool during laser welding. When the droplet filling position was increased from 0.5 mm to 1.8 mm, the influence on the three-dimensional shape change of keyhole was weakened. The flow trend that the front and rear walls of the keyhole was squeezed inside the molten pool to drive the keyhole to close was weakened, while the flow tendency of maintaining the keyhole wall opening was enhanced, and the fluctuation amplitude of liquid metal flow velocity at the bottom of keyhole was weakened.