The invention provides a control method for the stability of a sublance rotating mechanism. The whole rotating mechanism is supported by taking a speed reducer shaft of the sublance rotating mechanism as a supporting point, no any other mechanical supporting equipment or fixation is additionally arranged, and two calculating methods including a PLC (Programmable Logic Controller) internal calculating method and a frequency converter calculating method are combined to be applied, so that the stable operation of the sublance rotating mechanism is realized. By using the control method for the stability of the sublance rotating mechanism, which is provided by the invention, the stable operation of the mechanism can be ensured, and meanwhile, no any other mechanical supporting equipment or fixation is additionally arranged, so that the equipment maintenance and cost can be reduced, and the equipment utilization space can be saved.