Engineering ceramic is the ideal material for high-speed and high precision motorized spindle due to perfect characteristics of light weight, wear resistance, high temperature, high strength, and so on. The air-gap is changed due to the influence from various factors not only the tolerance of the manufacture and assembly of motorized spindle but also different working condition. The change of air-gap impacts on vibration performance of motorized spindle. The effects of rotating speed and air-gap between the rotator and stator on these characteristic parameters of the motorized spindle are analyzed. This paper analyses the effect change of air-gap on vibration performance of motorized spindle by the simulation analysis and experimental. The results show that vibration increase with the decrease of air-gap. Meanwhile, electromagnetic vibration increase with the increase of eccentricity of motorized spindle. These results are very helpful to the structure optimization and application of the ceramic motorized spindle.