In order to research aerodynamic characteristic of missile during stage separation, in this paper, missiles' separation process was simulated by a numerical calculation program which was exploited independently, and partial tests were finished in the wind tunnel, the trend of the missiles' aerodynamic characteristic in the process was analyzed. The research range of the Mach number is 2.0 to 5.0 and the angle of attack is 0° to 6°. The results show that the angle of attack and the angle of sideslip have less affection on missiles' axial displacement, the bigger is Mach number, the smaller is cone angle of grade I and the ratio of grades' diameter is close to 1.0 are benefit for missiles' fast separation.