<p>Hybrid stepping motors (HSMs) are commonly used for the part in the industry, because HSMs have high torque and resolution advantages with comparing with other types of stepping motors. In this paper, a radially magnetized stator-permanent-magnet HSM (RMSPMHSM) with four poles (FP) is proposed, and compared with that with two poles (TP). Firstly, the structure of the RMSPMHSM with FP is introduced and its operation principle is analyzed by describing the variation of stator pole polarity with current. Secondly, based on the same electrical load and the amount of PM, the RMSPMHSM with FP is designed. Thirdly, the electromagnetic characteristics of the two motors are analyzed, including PM flux linkage, back-electromotive force, detent torque, holding torque, output torque and so on. Finally, the simulation results indicate the RMSPMHSM with FP can solve the problem of PM flux linkage asymmetric, and has higher torque density than RMSPMHSM with TP.</p>