In order to reduce the water level or water pressure in the soil below the water body, an unconventional water descent technology is proposed to ensure the safety of underwater engineering. Underwater dewatering technology is a new technology. Compared with land dewatering, its technical link is more complex and construction is more difficult. Through exploring and researching the technical difficulties, feasibility analysis, design calculation and determination of soil parameters of a project in the process of construction of water descent, A series of innovative technologies are adopted, such as waterproof casing technology, new waterproof material, underwater dewatering test model and casing stability analysis. Successful application of underwater dewatering technology has pioneered both at home and abroad. However, the construction of underwater dewatering is difficult and expensive. There are still some technical risks, and some technical links need to be further explored.