In thick oil reservoirs subjected to prolonged waterflooding development, the complex vertical water flooding patterns pose significant challenges to production optimization. Based on the principles of flow mechanics, an analytical model for vertical particle migration was established by integrating dominant controlling factors including viscous forces, oil-water density difference and interlayer distributions. The model enables precise and rapid calculation of waterflood front propagation velocities and trajectories between injection-production well during reservoir development. Furthermore, it effectively characterizes vertical water flooding pattern in thick oil reservoirs, providing a method for accurate determination of remaining oil distribution. The research shows that permeability ratio, liquid production rate, well spacing, oil-water density difference, stratigraphic rhythm and interlayer distribution exert significant control on water particle migration trajectories. These factors induce diverse vertical sweep characteristics, leading to dispersed remaining oil distribution patterns characterized by bottom water flooding and controlled by underlayers. The result provides targeted guidance for remaining oil production in thick oil reservoirs.