A stage light with a speed reducer including a light head, a supporting arm and a bottom box. The light head is pivotally connected to the supporting arm by a pivot shaft. The supporting arm is pivotally connected to the bottom box by a pivot shaft. The pivot shaft of the light head and/or the pivot shaft of the supporting arm is connected to a drive shaft of a driving mechanism by the speed reducer. According to the stage light with the speed reducer, the pivot shaft of the light head and/or the pivot shaft of the supporting arm is connected to the speed reducer drive shaft of the driving mechanism, thereby realizing using a transmission part in the speed reducer for transmission, avoiding using a synchronous belt. The transmission part will not deform and cause inaccurate scanning positioning or fracture, and the product performance is more stable.