The design and optimization of active phase of the missile are very important for improving the missile's firing range. Taking the two-stage missile as an example, the trajectory optimization model of missile active phase is established. Then, a hybrid algorithm based on simplex method and Genetic Algorithm (GA) is proposed according to parameter optimization theory. The algorithm not only has fine global convergence performance, but also has fast convergence speed and high precision. Finally, the effectiveness of the proposed method is demonstrated by experiments. Compared with the initial trajectory, the velocity at the end point of the active phase is increased effectively, and the range is increased by 32%. Hence it is proved that the proposed method is feasible and effective for missile trajectory optimization.