Abstract: An approach for GTO launch trajectory optimization design is proposed, which is consisted of bilevel programming method,trajectory decomposition optimization design and hybrid Genetic Algorithm. In order to overcome the poor convergence problems caused by the couple of system variables and optimal control variables, the bilevel programming model is set up, in which the master problem only deals with the system variables, and the junior problem only deals with the trajectory optimal control variables. The all-up launch trajectory optimization design problem is divided into two segment trajectory optimization design problems. The pipeline hybrid Genetic Algorithm is applied to solve the junior problem. As an example, maximal payload optimization design of a two-stage GTO launcher is completed, several problems such as how to choose pitch angle and how to choose parameters of launch trajectory are discussed, and several constructive conclusions are gained. This approach for GTO launch trajectory optimization has been testified with predominant performance index, and has great engineering value in launch vehicle system design.