In continuous casting production, droplet characteristics are important parameters for evaluating the nozzle atomization quality, and have a significant impact on the secondary cooling effect and the slab quality. In order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect, the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT software. Results show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center, thus, the liquid volume fraction in the center is higher than that of either side. As the droplet diameter increases, the region of high liquid volume fraction on the slab surface becomes wider, and the liquid phase distribution in the slab width direction becomes uneven. Although increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone, the distribution becomes more uneven due to more liquid reaches the slab surface per unit time. A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data. A nozzle spacing of 210 mm was recommended under the working conditions in this study, which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.