Hengsha east shoal is a large mouth bar in Yangtze estuary. The main problem of building large excavated-in deepwater harbor basin here is the maintainability of the basin and waterway. In this paper, on the basis of the characteristics of current and sediment, the basin and its entrance sites selection and the maintainability of the basin and waterway are discussed. The results show that the entrance of the basin should be set in the east side of Hengsha east shoal and on the south of Jigu reef, and towards southeast. The entrance and waterway should be built in the area where the depth is greater than 10 m. If do so, the tidal prism is large; the siltation is small, and the maintainability is good.