Aerodynamic design of launch vehicle is facing combinatorial explosion problem caused by modular design. In order to get basic feasible solution from huge design space, the efficiency of design and simulation must be improved. In this paper, a parametric modeling and simulation method is proposed, which is based on CAD/CFD tools. Firstly, the design Variables of the launch vehicle are divided into three categories: size parameters, configuration parameters and mesh parameters. Secondly, parametric geometry model, including size and configuration parameters, is obtained by secondary development of Pro/ENGINEER. Thirdly, parametric mesh files for CFD are generated by implementing CFD-GEOM with scripts written in Python. By specifying boundary conditions through command stream of GAMBIT, FLUENT software will run automatically to calculate the aerodynamic performance of the launch vehicle. Finally, a graphical user interface (GUI) is developed using VC++6.0. With this system, the integration of CAD/CFD application is achieved. As long as designers enter certain design parameters in the GUI, they will quickly achieve 3D geometry model and aerodynamic performance of the launch vehicle. Application examples show that, this system can significantly improve the efficiency of aerodynamic design of the launch vehicle, and the data error between simulation and experiment is less than 10%, which is acceptable.