The invention relates to the field of automatic production, in particular to a floating support control system and method for a workpiece. The floating support control system comprises a rotating device, a height-regulating device and a processing unit, wherein the rotating device is used for fixing the workpiece and driving the workpiece to rotate; the height-regulating device comprises a supporting platform and a motor connected with the supporting platform and used for driving the supporting platform to float up and down, and the supporting platform is propped against the lowest point of the rotating workpiece; and the processing unit acquires the movement track of the lowest point of the rotating workpiece according to the cross section shape of the workpiece and the rotational speed of the rotating device and controls the motor to drive the supporting platform to float up and down along the movement track. When the workpiece rotates, the motor drives the supporting platform to float up and down, and the workpiece is supported at the lowest point on the surface of the workpiece. According to the floating support control system, the supporting lowest point on the surface of the workpiece is controlled in real time, so that the workpiece is prevented from shaking during high-speed rotation, and accordingly, the processing precision of the rotating workpiece is improved.