Suspended rotor displacement fluctuation would result in unbalanced magnetic pull and inaccurate speed measurement, which degrades the suspended rotor stability and motor performance. In order to reduce the blight, some research studies have been conducted. First, the influence on the motor magnetic field has been analyzed between motors with iron-cored and coreless stator structures. It is found that with the coreless stator, the air-gap magnetic flux density variation can be neglected. Second, the law of the speed fluctuation caused by the rotor runout has been studied. In addition, two methods, which are based on the use of notch filter and speed correction, have been proposed for suppressing the fluctuation. Third, the performances of the closed-loop systems with the proposed speed fluctuation suppression methods have been analyzed. Finally, experimental results are presented to demonstrate the correctness of the analysis and the validity of the proposed methods.