Abstract: As cities are constructed on geological objects, the support of Urban Geology (UG) is necessary for the city construction and development. Urban 3-D geological modeling (U3DGM), a classic application of 3-D information technology to UG, plays an important role in improving the UG achievement expression and urban geological resources and environment assessment. In addition, it may play an important role in supporting the ongoing urbanization in China. In this paper, the authors firstly make a classification and characteristic analysis of urban 3-D geological models. Secondly, the construction of urban 3-D geological models is studied, with more details given to the construction of urban 3-D geological framework models. At last, on the basis of the research in this paper, the applications of U3DGM in the city plan are presented in such aspects as subway and tunnel location, new town construction, key projects location and resource development of Beijing.