Abstract: The South-to-North Water Diversion Middle Route Project is a strategic infrastructure to alleviate the shortage of water resources in the north,and the project has played a huge comprehensive benefit. The water transmission line of the project is long and there are many river canal crossing buildings. With the increase in project operation time,affected by adverse factors such as freeze-thaw change,concrete carbonization and sediment deposition,the unevenness of the overflow surface of water transmission buildings increases gradually,which may pose a certain risk to the overflow capacity of the water transmission system. Combined with the characteristics of the middle line project,this paper selects the typical water conveyance aqueduct as the test object,and explores and studies the spraying of a non-toxic,harmless and stable nano material on the surface of the building,in order to protect the concrete and reduce the surface roughness of the building at the same time. According to the actual operation of the project,the cooperation scheme of test flow measurement,detection and dispatching is proposed,which is successfully implemented on the premise of ensuring normal and safe water supply. The flow pattern comparison before and after the test and hydraulic simulation calculation is carried out,and the test effect is analyzed and evaluated. The results show that this method can improve the water flow pattern of aqueduct,reduce the surface roughness of aqueduct and improve the flow capacity. The study can be used as a reference for roughness reduction and protection of similar long-distance water transfer projects.