Abstract: The 3D geological modeling for the complex geologic bodies is an essential technique of the urban geology. The accuracy of 3D model, for engineering analysis, judgment and decision has great influence. A new method for 3d geological modeling is introduced, which is based on the “structures mosaic” technique. The key technology and modeling process of urban geological 3D modeling on complex fault conditions are discussed. A case study of geological model in Guanzhong basin is presented, which confirmed that, this method can effectively improve the efficiency and accuracy of complex structures condition, and can provide reference for the areas of complex geological conditions in urban geological survey.