As the main load-bearing structure of a bridge, the underwater foundation is an important component to ensure the normal and safe operation of the bridge structure. It not only bears the dead load and live load of the bridge but also transfers them to the foundation. Therefore, its working condition directly affects the load-bearing capacity of the bridge. Once problems occur, it will bring major safety hazards to the bridge and even lead to its collapse. However, due to the long-term exposure of the underwater foundation in complex hydrogeological conditions, its usage conditions and environment are more severe than those of the above-water structure. It especially needs to withstand the long-term scouring of water flow and is also affected by human activities such as large-scale sand extraction in rivers in recent years, which can change the free length of the pile body. All these factors can easily lead to various diseases in the underwater foundation of the bridge. These diseases are not easy to be detected during regular inspections and are becoming more serious and widespread, which can easily lead to a reduction in the load-bearing capacity and durability of the bridge. In severe cases, it may even threaten the operational safety of the bridge. Therefore, to ensure the safety of transportation, it is an urgent task for the highway department to conduct regular physical examinations of the underwater foundation of the bridge, timely grasp its health status, and carry out research on underwater pier detection technology.