Abstract: Due to the long-term water erosion on the water pile foundation, the effective depth of the Donghai Bridge pile foundation into the soil has been progressively diminishing year by year, leading to the pile foundation instability and posing a potential threat to the overall safety of the building. Based on the protection project of bridge pile groups, the ratio of the stabilized soil slurry was investigated and determined. Subsequently, the high flow stabilized soil protection construction was successfully completed. The underwater pumping construction process, the outcomes of the stabilized soil protection construction, and its long-term protective effects were analysed. The results indicate that as the amount of curing agent increases, the strength of the stabilized soil increases while its fluidity decreases. Conversely, as the water content of the slurry increases, the strength of the stabilized soil decreases while its fluidity increases. The underwater high-definition sonar can observe the relative positions of underwater pile foundations and pumping pipe in real time, effectively guiding underwater construction. The underwater ejection distance of the stabilized soil slurry is approximately 2.5 meters, with both the flowing distance and width exceeding 3 meters. The lowest point of the projected centreline of Pier PM123 has been backfilled by approximately 4.3 meters, and the lowest point of the projected centreline of Pier PM230 has been backfilled by approximately 5.4 meters. The stabilized soil protection construction can effectively backfill the gaps between pile groups and depressions at the bottom of the pit, forming a smooth stabilized soil protective layer with excellent erosion resistance and long-term durability. This engineering practice could accumulate experience for similar projects and provide data support and technical reference.