An active fault-tolerant flight control system was designed in view of actuator deadlock, driver circuit failure, servo motor failure and other rudder faults of air-to-air missile. The inherent connection and functional redundancy among control surfaces of tail fin of missile were used and the distribution of control instruction was changed to achieve tri-channel autopilot stability design, simulation results indicate this method has strong fault-tolerant capability for typical actuator fault problems; the reliability of air-to-air missile control system is improved.