An internal rotary structure of a crystal ball seat having a base plate, a rotary disk, gears and other components; characterized in that: a circular platen is formed on the center of the upper surface of the base plate; a rotary disk is installed on the periphery of the platen of the base plate; circular teeth formed on the inner rim of the rotary disk, and a driving gear of longitudinal axis is installed below the driving gear of the music bell rolling wheel. By this structure, in a small space, the rotary disk may be used to drive the music bell.