Abstract: The serious problem of foundation scouring commonly existing in offshore wind turbine piles significantly affects the safety of wind power foundation structures. Therefore, it is necessary to conduct in-depth research on the protective measures for offshore wind turbine piles. Using numerical simulation methods, the protective performance of scour protection rings for single pile foundations under unidirectional flow conditions was studied. A numerical model of the interaction between water flow, pile foundation/protection ring, and seabed was established in the FLOW-3D software. The study analyzed the influence of two parameters, the diameter and installation height of the protection ring, on scouring. Based on the numerical simulation results, a predictive formula for the scour depth under protection by the protection ring was proposed. The research findings indicate that the closer the protection ring is to the bed, the higher the protection efficiency for protection rings of the same diameter. When the installation height is 0.04 m, the scour depth decreases by 50%, and the highest protection efficiency is achieved when the installation height is 0 m. There is a failure zone for protection by the protection ring, and when the protection ring is too far from the bed, it basically loses its protective function. For protection rings installed close to the bed, the larger the diameter, the better the protection efficiency. When the diameter of the protection ring is 0.30 m and 0.35 m, the reduction in scour depth is both greater than 50%. However, beyond a certain limit, with the increase in the diameter of the protection ring, the time to reach scour equilibrium also increases accordingly, but the protective effect of the protection ring hardly changes.