The present invention discloses a control method and device of restraining sub-synchronous resonance, wherein the method comprises the steps of selecting an input signal of an additional damping controller; determining the access position of the additional damping controller; carrying out the filtering, proportional phase shift and amplitude limiting operations on the input signal to obtain an output control signal; restraining the sub-synchronous resonance of a system according to the output control signal and the access position. According to the method of the present invention, the sub-synchronous resonance of the system is restrained effectively, and the safe and stable operation of a draught fan and the system is guaranteed. The present invention also provides a control device of restraining the sub-synchronous resonance.