Abstract: The system parameter design combining with the trajectory optimization design can efficiently improve the whole design performance of launch vehicle during its preliminary design. Considering engineering requirement a set of mathematical models for trajectory and system parameter integrated optimization design are developed. The optimization methods for launch trajectory of low earth orbit are discussed, and the optimal control problems are converted into parameter optimization problems by multiple parameterized methods. An adaptive combinatorial optimization algorithm for solving this integrated optimization design problems is put forward. The results show that the total takeoff mass, which is a very important index in designing launchers, can be reduced by 3 5%. The optimization models and corresponding software presented in this paper has been successfully applied in the engineering design.