Considering the development trend of the metal structure design, such as the modularization of characteristic dimensions, typification of structures, univeralization of spare parts, serialization of parameters, as well as modularization of the assembly, we put forward the principle of modularization-based design in the metal structure of ship lock through the study and exploration during the design work of both Beijing-Hangzhou canal project and the Ganjiang river ship locks project, which is of great significance in improving the quality and efficiency of the metal structure’s design, enhancing the commonality and exchangeability of the metal structure, expediting the process of standardization and serialization of the ship lock, and accelerating the development of navigation industry.