Firstly, the author discussed the general application patterns of GIS (Geography Information System) in hydrology and water resources. Using relaxed combination mode of GIS and hydrological models, the GIS platform of water cycle of the Yellow River basin was established with MS-Visual Basic visualized developing language based on ESRI-MapObject GIS component. All kinds of data related to water cycle of the Yellow River basin were saved in the platform with uniform coordinate and uniform format, which supplies data support for the study of water cycle elements and process of the Yellow River basin.