Interior permanent magnet synchronous motor (IPMSM) has stronger reluctance torque and mechanical strength and better dynamic performance, being highly suitable for high-speed operation. Practically, the performance of IPMSM is dramatically influenced by various rotor structures. This paper studies a fractional-slot IPMSM and it is analyzed that how those parameters, such as the number of permanent magnet segments, the width of magnetic bridge and the thickness of flux barrier, etc., impact on the motor characteristics, namely, no-load back electromotive force (BEMF), dq-axis inductance, cogging torque and speed regulation range, and so on.