Smart water conservancy is the most significant symbol of high-quality development of water conservancy in the new stage and one of the six implementation paths. The data base is an important support for smart water conservancy construction. In view of the problems existing in the water conservancy data of Jiangxi province, such as insufficient integration, inconsistent basic data, inconsistent data standards, and insufficient internal and external sharing etc, this article takes the construction of digital twin water conservancy data backplane in Jiangxi province as an exampleto propose the target positioning, construction ideas, and key capabilities of the data base. It realizes the provision of data services for water conservancy departments at all levels and cross-industry departments, and provides extensive data services for intelligent water conservancy and digital twin application scenarios such as flood control and drought resistance, water resource allocation, and water engineering safety management for departments at all levels.Finally, It effectively improves the "data calculation" support capability, and the relevant practices can provide reference for the construction of digital twin of water conservancy data base.