The composite bucket foundations (CBFs) of offshore wind turbines exhibit a shallow depth into the seabed, making local scour a significant threat to wind turbine stability. In this study, a physical model was established to investigate the local scour around a new-type mono-column composite bucket foundation (MCCBF) under both steady flow conditions and combined flow-wave conditions. Subsequently, the protective effectiveness of the wing slab surrounding the MCCBF was evaluated. The experimental results demonstrated that the local scour topographies exhibited significant differences between steady flow conditions and combined flow-wave conditions. Waves generated frontal and lateral scour pits around the foundation, and enhanced both the scour depth and range. Under steady flow conditions, installing wing slabs around the bucket foundation provided an effective protective effect. However, under combined flow-wave conditions, the wing slabs tended to separate from the bed surface, leading to the exposure of bucket foundation.