To solve the fault-tolerant control problem of uncertainty, control surface faults and saturation for Reusable Launch Vehicles (RLVs) during reentry, a back-stepping control strategy based on Fixed-Time Disturbance Observer (FTDO) combined with auxiliary anti-saturation system is proposed.Firstly, a FTDO based on the super twisting theory is designed, which not only ensures the accurate estimation of disturbance, uncertainty and actuator faults in the system, but also effectively improves the estimation accuracy of the disturbance with variable frequencies.Secondly, an auxiliary compensation system based on anti-windup technology is devised to make the control surfaces exit saturation state as soon as possible, so as to tackle the problem that the control surfaces are liable to be saturated during RLV reentry.The simulation results show that the fault-tolerant control method can effectively solve the problems of faults and saturation of control surfaces, suppress disturbances and uncertainties, and improve the control accuracy and robustness of the attitude control system during RLV reentry.