Abstract: Faced with the energy crisis and the need to reduce ship emissions, underwater drag-reducing coating technology has become an important approach for improving navigation efficiency and reducing frictional resistance. A systematic review of the classification and drag reduction mechanisms of such coatings is provided, including surface energy regulation, topography design, and lubricating interface principles of superhydrophobic, superhydrophilic, biomimetic and nanocomposite coatings. The principles, advantages, disadvantages and applicability of laboratory methods, such as rotary rheometer tests, water tunnel tests and underwater hydrophilicity tests, as well as field test methods like plate resistance tests and towing tank experiments, are analyzed in detail. Current challenges related to coating performance, such as air layer stability, mechanical durability and environmental adaptability, are summarized. Finally, the development directions for multifunctional integration, intelligent adaptability and environmentally friendly coatings are prospected, aiming to provide a theoretical reference for the design and performance evaluation of drag-reducing coatings for ships.