The radiation noise characteristics of three motorized spindles were researched. The radiation noise of the motorized spindles was measured by experiments,and the time-frequency characteristics of the radiation noise of the motorized spindle with full ceramic bearings, with steel bearings and without inner ring bearings were analyzed by the experimental data. The experimental results show that with the increase of rotation speed, the radiation noises of the motorized spindles with full ceramic bearings and with steel bearing have an increasing trend, and the radiation noise contains the characteristics of rotational frequency and double rotational frequency. While the radiation noise of the motorized spindle without inner ring bearings changes in a fluctuation form, and its sound pressure level is higher than that of the other two motorized spindles and the spectrum is disorderly. At a high speed, the sound wave of the motorized spindle with full ceramic bearings has an obvious periodicity. The three motorized spindles have high friction and impact noise.