The middle route of the South-to-North Water Transfer Project is an extremely large water transfer project in China, with many cross-building, complex engineering environment and geological conditions. The durability design of the engineering structure is an important guarantee for the lasting and safe operation of the project. In this paper, Nansha River inverted siphon, a large canal crossing structure in Hebei Province of the Middle Route of the South-to-North Water Transfer project, is selected and the basic idea of durability design is briefly introduced. It provides reference for the design of similar buildings.