Abstract: Ecological water requirement is one of the important components of regional water requirement, and is a base for sustainable development of irrigated region. Under the analysis of precipitation, runoff and groundwater resources, the ecological system in Tongzhou District, Beijing was subclassified using geological information system(GIS) technique, the water requirement of various types of ecosystem were determined. Results indicate that the ecological water requirement is 45.33×10⁶ m³/a in Tongzhou District in 2003, and total water requirements of daily life, ecosystems and production is 1.23 times of the available water amount. The shortage of water resources is serious in Tongzhou Districe. After the adoption of water-saving techniques, the exploitation of new water sources and water-conveying from other regions, the water requirement of daily life, production and ecosystem can be basically satisfied in 2010 and 2020. Balance between water requirement and water supply in the studied region is realized. The research provides a scientific basis for reasonable allocation of water resources in Tongzhou District.