Abstract: The spatial data model of GIS is the core and basis for its application in hydrology and water resources management. In combination with the current practice and requirements, two kinds of hydrological data models of GIS were analyzed and summarized. The spatial and temporal distribution features of the hydrological variations were deeply discussed and explored during the process of constructing hydro - spatial database of GIS. Finally an object - oriented hydrologic data model of GIS was presented.