One of the most important structural problems for permanent magnet synchronous motors is the cogging torque. One of the most effective ways to reduce the cogging torque is that magnets or slots are skewed. However, this will negatively affect the motor cost and production time. On the other hand, the cogging torque depends on the change in the reluctance of the motor in the air gap during operation. Therefore, the most important design approach to reduce the cogging torque is to examine the parameters that affect the air gap reluctance. In this study, the change of air gap reluctance of surface mounted permanent magnet synchronous motor with outer rotor during operation is investigated. For this purpose, the five most important parameters affecting the air gap reluctance change are selected. In this way, the best motor model with low cogging torque is tried to be obtained.