Digital city is one of the important branches and regional layers of digital earth. The modeling and simulation of a city can visualize the city in the computer and therefore improve the management of the city. How to model and simulate the city in a three dimensional scale with the seamless link between spatial geometry and attribution has become the hot topic of experts from both virtual reality and geographical information system fields. This paper designs a platform of three dimension modeling and simulation for digital city. This platform consists of several modules such as Data Acquisition, Data Import & Export, Database Management, Model Edit & Reorganization, and Scene Create & Cruise. The most important input data resources used in this platform are DXF and 3DS, which are obtained and produced from the digital stereo photos taken by the Data Acquisition Module(Z-system). The Import & Export Module converts the DXF and 3DS data into OpenFlight format, and then by using the Model Edit & Reorganization Module, the converted models can be visually edited and reorganized so as to recreate more rational models with both spatial and attribute information stored in the Database Management Module. The Scene Create & Cruise Module selects models from the database to create three dimensional scenes of the city and provides the interactive cruise and information query in the scenes of the city. It is concluded that this platform integrates the technologies of geographical information system, virtual reality and database, and can play the role of the base of digital city onto which other application systems are joined.