This paper presents an urban water supply network system based on GIS technology. The system will adopt three-tier/N-tier architecture as the application logic structure. Thy system can be divided into six subsystems: the analysis subsystem, the aided design subsystem, the installation and maintenance management subsystem and the customer service subsystem serve data management subsystem. The data management of the system will adopt SuperMap. We present the details of the data management, such as basic data collection, structure framework of the basic geographic information bank, the process to construct GIS basic information bank of water supply network, data conversion and input into banks, data vectorization and input into banks, etc. Then the system database is designed in detail. We adopt object oriented analysis and design methods, and utilize Class Diagram of UML to represent the entity tables and their relations against the core data of the network system, that is spatial dictionary database and spatial database. According to Class Diagram, it can be directly mapped as the database structure and an example is given. Finally, the successful application of the system in Yiyang city of China is beneficial for water supply enterprises to utilize the existing water resource in time, rationally and effectively.