Real-time calculation of dynamics model is one of the key technologies in the driving simulator. A multi-body dynamics model of tracked vehicle was developed using the Vortex software. The sinusoid superposition method was exploited to extend the 2-D road surface spectrum and to establish the 3-D road roughness elevation data in accord with the state standard. Then the elevation data were imported into Multigen Creator to construct the 3-D virtual road. Including the vehicle model, the virtual reality system was created. In the simulation of riding comfort, the responses of the vehicle were obtained when the vehicle traversed under road excitation of D grade with constant speed. The result shows that the system offers good immersion and real-time performance. It is feasible to be applied to the tracked vehicle driving simulator.