A rapid multidisciplinary design optimization method based upon sensitivity analysis is developed to address the matter of the high computational complexity and low efficiency in launch vehicle optimization with multiple stages. First, a multidisciplinary design optimization approach for the launch vehicle with solid rocket motors is established with the effort of minimizing the takeoff mass by employing genetic algorithm. Multiple disciplines that include propulsion, geometry and aerodynamics, mass and trajectory are integrated to produce the launch vehicle system model. Then, sensitivity analysis based upon the orthogonal experiment is conducted on the design parameters of the launch vehicle with respect to takeoff mass. The range constraints of each design variable are set reasonably according to the sensitivity analysis. The simulation results indicate that the method proposed can achieve a dynamic balance between the convergence time and performance index, and significantly improve the computational efficiency while preserving the quality of the solutions.