In view of the shortcomings of the current simulation systems in fidelity and real-time capability, and the lack of data for generating a digital terrain model, the construction drawing is used for a data source, with Auto CAD to be used for modeling. By a data conversion module of polytrans, the data in the standard format are obtained. Then, the solid model is imported into Creator/Vega to do the texture paste and scene synthesis for the simulation system. In the process, the landscape design scheme can be customized and changed, and a secondary development platform can be used to extend the applications of the data analysis module. The overall framework of the virtual simulation system based on AutoCAD and Creator/Vega is thus constructed. The application scopes of four terrain conversion algorithms are analyzed. The traditional information of design files, such as floor plan, longitudinal section and cross section, is extracted and used in the three-dimensional modeling of the main road. At last, the real-time simulation is achieved. Simulation results are realistic, and can be adjusted in real time.