The invention provides a device and a method for preparing deposited modified coating layers on the surfaces of precise balls, and belongs to the field of surface preparation of the precise balls. A support rolling body is placed in a rolling body keeping ring; a spherical joint connected with a spherical swing device is connected with a central shaft through threads; a rotating disc is connectedwith a rotary worktable base through bolts; the precise balls are placed in a motion rail in the connected place of the rotating disc with the spherical swing device; the rotary worktable base drivesthe rotating disc to rotate, so that the precise balls are rotated around a Z axle; meanwhile, an inclined surface on the rotary worktable base drives the spherical swing device to repeatedly swing, so that the precise balls are rotated back and forth around a Y axle; and through free rotation in the two directions, random rotation of the precise balls is realized. The method comprises the following steps: precise ball parts are placed in a rotating device; splashed positions of the precise balls are adjusted by using continuous rotation of the device, so that the overall surfaces of the precise balls can uniformly receive injected ions.