A fault-tolerant control scheme based on command filtered backstepping method is proposed for the failure of a single motor in a four-motor servo system. Firstly, a dynamic model of the fault servo system with unknown inertia and unbalanced torque is established. Subsequently, the controller is designed using command filtered backstepping technology, in which an error compensation system is designed to improve the control accuracy. In addition, the neural network is used to deal with the nonlinear disturbance caused by the faulty motor, and synchronization error signals are designed to achieve synchronization control of the system. Finally, based on the Lyapunov stability theory, the stability of the closed-loop system under the condition of single motor failure is proved. And simulation is designed to verify the effectiveness and superiority of the proposed control method.