The Digital City Construction is an important part of the city information construction. With the development of information technology, on the three-dimension models of digital city put forward higher requirements, higher requirements of 3D Digital City have been proposed. However, the existing 3D modeling tools could not meet this demand. Fortunately, the development of BIM has provided a more accurate measure for 3D model of the Digital City. By analyzing the difference between BIM and GIS, The article discusses the application of BIM technology in the 3D modeling of the Digital City in terms of data organization and application.