Range is one of the most important performance taget of the ballistic missile. The purpose is to get the maximum range by modifying the flight program under the condition of specific parameters of ballistic missile were given. Considering constrains of the whole flight trajectory of the ballistic missile,a mathematical model of maximum range optimization was built,a corresponding simulation model was also built under the MATLAB/SIMULINK environment. As an example,maximum trajectory optimization was applied on a two-stage ballistic missile,and a comparison of original and optimal trajectories was presented with figures and tables. The results demonstrate that the method given by this paper is all-purpose and feasible.