Abstract: 3D Geological modeling technology can more intuitively represents the 3D structures and spatial distribution of rock formations of subsurface, when it is compared with traditional 2D geological mapping technology. It has important applications in planning, design, construction and risk assessment of the engineering projects. Modeling objects often involves complex geological bodies in engineering fields. In order to improve the automatic level of 3D geological modeling, this paper proposes an automatic method of modeling complex geological bodies based on ArcGIS Model Builder. First, the borehole data and geological section maps are used as data source. The Python object-oriented programming language and ArcPy package are combined for automatic preprocessing of the drilling data. Secondly, the function of automatic vectorization of ArcScan and the human computer interaction (HCI) of SkechUp are combined for extracting the 2D and 3D fault lines and then stored in GIS spatial database. Thirdly, the Model Builder of ArcGIS, a visual modeling tool, is used for automatically creating the 3D solid models of strata and the 3D surface models of faults using the data processing, file conversion and 3D analysis tools of the ArcToolbox. Fourthly, the cutting, cross-section and excavation polygons are vectorized respectively as the inputs of the 3D analyst tool of Extrude between extended using ArcPy. The 3D visualization tool of ArcScene is used for realizing multiple types of visualization. Finally, the drilling data acquired from the 3D geological survey in Nanjing Xianlin area are used for practical modeling test. The modeling results show that the method has accurate, rapid and automatic advantages, which can provide reliable technical solutions for large-scale and mass geological modeling.