A five-phase dual-rotor permanent-magnet synchronous motor (PMSM) used for electric vehicles is investigated in this paper. The dual-rotor PMSM consists of an inner motor and an outer motor, which share a common stator yoke. The magnetic coupling exists not only within the interphases, but also between the inner and outer motors, which leads to control complexity and affects performance and fault-tolerant capability of the motor. Thus, the electromagnetic characteristics, particularly themagnetic-coupling characteristics of the dual-rotor PMSM, are investigated based on magnetic circuit and finite-element methods. The influences of magnetic coupling caused by the structural arrangement (pole/slot combination, magnetization type of PMs, armature reaction, common stator yoke thickness, and winding structure) are analyzed in this paper. Then, a magnetic decoupling design is introduced for the five-phase dual-rotor PMSM. A prototype was manufactured and tested to verify the validity and accuracy of the process presented in this paper.