The neutral point, center of gravity and flight attitude of the carrier aircraft will change dramatically after the separation of the combined aircraft. Aiming at this problem, this paper studied a flight control method suitable for combinational aircraft and carrier aircraft. The state space model including tracking signal is established, and the longitudinal/lateral heading flight control law suitable for the composite aircraft is developed by using the robust servo. The control law is composed of guidance loop/angular outer loop and angular rate inner loop, and the robustness of the system to external disturbances is improved by integrating in the inner loop of the angular rate. The closed-loop system characteristics are analyzed using the frequency domain method, and the validity and robustness of the control law are verified by Monte-Carlo simulation in time-domain under consideration of various error sources. Finally, a verification flight test of the combined aircraft is carried out. During the flight, the carrier aircraft and the child aircraft are separated safely, and the attitude is controllable throughout the flight. This further verifies the reliability of the robust servo flight control law proposed in this paper.