Abstract: The operation principle of the five-phase fault-tolerant flux-switching permanent-magnet（FT-FSPM） motors was analyzed from the perspective of air-gap magnetic field modulation. The magnetic flux densities of 10/18 pole and 10/19 pole FT-FSPM motors which generated by the permanent magnet and the armature winding respectively were analyzed and calculated, and validated by finite element analysis. The magnetic field is generated by the PMs and the armature windings respectively. When the field harmonics and the rotational speed are both the same, these harmonics can be called the effective working harmonics. On this basis, the ratio of the torque generated by the effective working harmonics to the total average torque was analyzed by the air-gap magnetic field modulation theory. It is revealed that the five-phase FT-FSPM motors generate electromagnetic torque from some effective working harmonics, and these harmonics produce greater than 97% of the average electromagnetic torque. Experimental results verify the analytical and simulation results.