Abstract: Monopile foundations have become the most common infrastructure in the field of offshore wind power due to their simple structure and convenient construction. However, they are often accompanied by local erosion of the seabed around the pile. In this study, a spoiler anti-erosion structure is proposed, and a three-dimensional numerical model is established using a large-diameter monopile foundation of offshore wind power as the research object. Based on numerical simulations, the influence of the spoiler structure on local scouring around the pile is studied under constant currents. The influence of the spoiler’s length（L） and height（H2） on the position and strength of local horseshoe vortices is discussed, and the effect of local bed shear stress is also analyzed. Results show that the spoiler structure can effectively weaken the strength of local horseshoe vortices, reduce shear stress on the bed around the monopile.The local horseshoe vortex exhibits three flow mechanisms under the influence of the spoiler’s geometry. When L/H2=1, the spoiler has better erosion protection characteristics. Overall, the spoiler structure has a good protective effect on local erosion protection and is significant for guiding the protection design of pile foundations.