Air-to-air missile launch by ejection puts higher requirement for attitude control of missile. The separation trajectories by which a missile ejected from an aircraft were computed by combination of numerical simulation based on N-S equations solver with motion equations of missile and control law. The computational results show that attitudes of static instable missile are divergent quickly due to aerodynamic interference by the aircraft and it is disadvantageous to missile's separation from aircraft safely. When attitude control strategy has been introduced, attitudes of missile during the separation from aircraft are effectively controlled, and security of missile ejected from aircraft is greatly improved.