A water-cooled roll is the core component of single-roll continuous casting technology for lead sheets, and its cooling effect directly affects the thickness control and quality uniformity of lead sheets. On the basis of the single roll continuous casting process, a three-dimensional numerical simulation of a water-cooled roll was carried out via ANSYS Fluent software, and the influences of different numbers of water outlet holes on the temperature field and flow field of the water-cooled roll were analysed. The results show that the distribution of the flow field inside the water-cooled roll is closely related to the number of water outlet holes, and the 24-hole design has the best performance in terms of the cooling effect and temperature uniformity, which can effectively control the thickness of the lead sheet and reduce the temperature fluctuation. The simulation results are verified by experiments. The lead sheet produced by the designed water-cooled roll prototype has a uniform thickness and smooth surface, which can meet the production requirements.