Abstract: Doubly Salient electro-magnetic machine (DSEM) has a broad application prospect in the fields of aviation and electric vehicles, both of which have higher requirements for the reliability. DSEM with separate excitation is realized by excitation winding, whose excitation fault is an important aspect that affects the reliability of the DSEM driving system. Aiming at the excitation fault of DSEM drive system, this paper proposes a torque ripple reduction strategy based on the vector control for fault-tolerant operation of the DSEM. First, according to the instantaneous power invariable principle, the torque model of the DSEM under excitation-loss is set up in polar coordinate system, which establishes the relationship between the reluctance torque and the amplitude and phase of current vector. Then, the phase of the current vector is determined for copper loss minimization, and the torque ripple is reduced by controlling the amplitude of the current vector. The three-phase reference current is obtained from the transformation of the current vector, which is utilized for the current closed loop control. Finally, the experiments are implemented on an 18/12 pole DSEM to validate the feasibility and effectiveness of the proposed method.